# Quiz 4: Newtons Laws

Physics & Astronomy

Q 1Q 1

According to Newton's law of inertia,
A) objects moving with an initial speed relative to a given frame of reference eventually come to rest relative to the reference frame.
B) whether an object is at rest or is moving with constant velocity depends on the inertial reference frame in which the object is observed.
C) rest is the most natural state of motion.
D) an object at rest in a given frame of reference eventually finds itself in motion relative to the frame of reference.
E) forces always exist in pairs.

Free

Multiple Choice

B

Q 2Q 2

Newton's law of inertia does not describe the behavior of objects
A) in inertial frames of reference.
B) moving with constant velocity relative to a given frame of reference.
C) at rest relative to a given frame of reference.
D) moving in accelerated frames of reference.
E) moving in a straight line at constant speed relative to a given reference frame.

Free

Multiple Choice

D

Q 3Q 3

An inertial reference frame is one in which
A) Newton's first law describes the behavior of matter.
B) the law of inertia is not applicable.
C) there is a great deal of matter.
D) the object of interest is traveling in a circular path.
E) forces do not necessarily exist in pairs.

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Multiple Choice

A

Q 4Q 4

A physical quantity that is sometimes described as the measure of the resistance of a body to a change in motion is
A) force
B) mass
C) acceleration
D) weight
E) friction

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Multiple Choice

Q 5Q 5

Which of the following statements includes all the essential elements of Newton's first law?
A) A body at rest persists in its state of rest unless acted on by a non-zero net external force.
B) A body persists in its state of rest or of uniform motion in a straight line as long as the net external force remains constant.
C) For every action there is an equal and opposite reaction.
D) A body persists in its state of rest or of uniform motion in a straight line unless acted on by a non-zero net external force.
E) The acceleration of a body is proportional to the net external force acting on it and to the mass of the body.

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Multiple Choice

Q 6Q 6

When Newton's first law of motion is mentioned, you should immediately think of
A)
B) action-and-reaction forces.
C) inertia.
D) gravitational forces.
E) centripetal acceleration.

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Multiple Choice

Q 7Q 7

Which fundamental force holds the atoms together in a block of wood?
A) gravitational force
B) electromagnetic force
C) weak nuclear force
D) strong nuclear force
E) all the four forces

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Multiple Choice

Q 8Q 8

A body moves with constant speed in a straight line. Which of the following statements must be true?
A) No force acts on the body.
B) A single constant force acts on the body in the direction of motion.
C) A single constant force acts on the body in the direction opposite to the motion.
D) A net force of zero acts on the body.
E) A constant net force acts on the body in the direction of motion.

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Multiple Choice

Q 9Q 9

The figure below shows two forces, F

_{1}and F_{2}, acting on an object. Use the vector diagrams to answer the next questions. -Which force vector best represents the resultant force on the object? A) (1) B) (2) C) (3) D) (4) E) none of the vectorsFree

Multiple Choice

Q 10Q 10

The figure below shows two forces, F

_{1}and F_{2}, acting on an object. Use the vector diagrams to answer the next questions. -A third force is applied on the object so that the net force on the object is zero. Which force vector best represents the third force? A) (1) B) (2) C) (3) D) (4) E) none of the vectorsFree

Multiple Choice

Q 11Q 11

The figure below shows two forces, F

_{1}and F_{2}, acting on an object. Use the vector diagrams to answer the next questions. -A force accelerates a body of mass M. The same force applied to a second body produces three times the acceleration. What is the mass of the second body? A) M B) 3M C) M/3 D) 9M E) M/9Free

Multiple Choice

Q 12Q 12

The figure below shows two forces, F

_{1}and F_{2}, acting on an object. Use the vector diagrams to answer the next questions. -A force accelerates a body of mass M. A second body requires twice as much force to produce the same acceleration. What is the mass of the second body? A) M B) 2M C) M/2 D) 4M E) M/4Free

Multiple Choice

Q 13Q 13

A net force of 64 N acts on a mass of 16 kg. The resulting acceleration is
A) 16 m/s

^{2 }B) 0.51 m/s^{2 }C) 64 m/s^{2 }D) 9.0 m/s^{2 }E) 4.0 m/s^{2 }Free

Multiple Choice

Q 14Q 14

A particle with a mass of 200 g is acted on by a force of 4.5 N. The acceleration of the particle is
A) 90 cm/s

^{2}^{ }B) 2.3 cm/s^{2 }C) 0.90 km/s^{2 }D) 23 m/s^{2 }E) 9.0 m/s^{2 }Free

Multiple Choice

Q 15Q 15

A mass of 25 kg is acted on by two forces:

_{1}is 15 N due east, and_{2}is 10 N due north. The acceleration of the mass is A) 0.72 m/s^{2}, 56.3º north of east. B) 0.20 m/s^{2}, due east. C) 0.72 m/s^{2}, 33.7º north of east. D) 1.0 m/s^{2}, 33.7º north of east. E) 0.20 m/s^{2}, 56.3º north of east.Free

Multiple Choice

Q 16Q 16

A mass m is traveling at an initial speed v

_{0 }= 25.0 m/s. It is brought to rest in a distance of 62.5 m by a force of 15.0 N. The mass is A) 37.5 kg B) 3.00 kg C) 1.50 kg D) 6.00 kg E) 3.75 kgFree

Multiple Choice

Q 17Q 17

If you apply the same force to objects with masses M and 4M, the acceleration of the mass M is
A) the same as for the mass 4M.
B) four times the acceleration of the mass 4M.
C) one-fourth the acceleration of the mass 4M.
D) twice the acceleration of the mass 4M.
E) one-half the acceleration of the mass 4M.

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Multiple Choice

Q 18Q 18

An object is moving to the right at a constant speed. Which one of the following statements must be correct?
A) No forces are acting on the object.
B) A larger number of forces are acting on the object to the right than to the left.
C) The net force acting on the object is to the right.
D) No net force is acting on the object.
E) Just one force is acting on the object, and it is acting downward.

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Multiple Choice

Q 19Q 19

A force F produces an acceleration a on an object of mass m. A force 3F is exerted on a second object, and an acceleration 8a results. What is the mass of the second object?
A) 3m
B) 9m
C) 24m
D) (3/8)m
E) (8/3)m

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Multiple Choice

Q 20Q 20

A 10-N force is applied to mass M. The same force is applied to mass 4M. The ratio of the acceleration of the smaller mass to the acceleration of the larger mass is
A) 4 to 1
B) 20 to 1
C) 1 to 1
D) 1 to 2
E) 1 to 4

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Multiple Choice

Q 21Q 21

A fat cat, ever conscious of its weight, walks into an elevator and steps on a scale. The elevator begins to accelerate downward. While the elevator is accelerating, the scale reads
A) more than when the elevator is stationary.
B) more than if the elevator were accelerating upward.
C) less than when the elevator is stationary.
D) a negative value.
E) Insufficient information is given to answer correctly.

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Multiple Choice

Q 22Q 22

If force (in N), length (in m), and time (in s) were considered to be the fundamental quantities, the units of mass would be
A) s

^{2}/(N · m) B) m · s C) N^{2}· m/s^{2 }D) N · s^{2}/m E) m/NFree

Multiple Choice

Q 23Q 23

Which of the following statements is true?
A) The mass of a body is a quantitative measure of its inertia.
B) Mass is a vector quantity.
C) The mass of a body is directly proportional to the acceleration it is experiencing.
D) The unit of mass in the U.S. customary system is the newton.
E) The mass of a body is inversely proportional to the resultant force acting on it.

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Multiple Choice

Q 24Q 24

A ball of mass 2.0 kg is acted on by two forces, and . The magnitude of the acceleration is
A) 2.5 m/s

^{2}B) 3.9 m/s^{2}C) 4.6 m/s^{2}D) 5.1 m/s^{2}E) 5.8 m/s^{2}Free

Multiple Choice

Q 25Q 25

A ball of mass 2.0 kg is acted on by two forces, and . The acceleration vector of the mass is (in m/s

^{2}) A) B) C) D) E)Free

Multiple Choice

Q 26Q 26

A ball of mass 2.0 kg is acted on by two forces, and . At t = 0 s, the particle is at rest at the origin. The position vector at t = 2 s is
A)
B)
C)
D)
E)

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Multiple Choice

Q 27Q 27

A ball of mass 2.0 kg is acted on by two forces, and . At t = 0 s, the particle is at rest at the origin. The velocity vector at t = 2 s is
A)
B)
C)
D)
E)

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Multiple Choice

Q 28Q 28

The diagrams below show the application of a force F on a block of mass m. Which diagram(s) produces the largest acceleration on the block in the horizontal direction?
A) (1) and (3)
B) (2)
C) (3)
D) (2) and (4)
E) The acceleration is the same for all four.

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Multiple Choice

Q 29Q 29

An unknown force is applied to two unknown masses M

_{A}and M_{B}. Their accelerations_{A}and_{B}are measured. From these data we can determine A) the magnitude of only. B) M_{A}and M_{B}only. C) the magnitudes of , M_{A}, and M_{B}only. D) the ratio of M_{A}to M_{B}only. E) M_{A}, M_{B}, and the weights of M_{A}and M_{B}.Free

Multiple Choice

Q 30Q 30

The mass of a body that weighs 2.00 N at sea level is
A) 0.204 kg
B) 2.00 kg
C) 19.6 kg
D) 9.80 kg
E) 0.451 kg

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Multiple Choice

Q 31Q 31

Rachel has been reading her physics book. She takes her weighing scales into an elevator and stands on them. If her normal weight is 690 N (155 lbs), and the elevator moves upward at 0.25g and then down at 0.25g, what is the difference between the up and down scale readings?
A) 690 N
B) 520 N
C) 170 N
D) 345 N
E) 1.04 10

^{3}NFree

Multiple Choice

Q 32Q 32

The weight of an object is
A) the same as the mass of the object.
B) the quantity of matter in the object.
C) the mass of the object multiplied by the acceleration due to gravity at sea level, regardless of where the object is located.
D) the result of the gravitational force acting on the object.
E) the reading on a spring scale attached to the object.

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Multiple Choice

Q 33Q 33

A body is sent out in space. Which of the following statements is true of this body as it moves away from Earth?
A) The body's mass and weight remain equal.
B) The body's mass remains constant, and its weight decreases.
C) The body's mass decreases, and its weight remains constant.
D) The body's mass and weight decrease.
E) The body's mass decreases, and its weight increases.

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Multiple Choice

Q 34Q 34

A person of weight w is in an upward-moving elevator when the cable suddenly breaks. What is the person's apparent weight immediately after the elevator starts to fall?
A) w
B) greater than w
C) less than w
D) 9.81w
E) zero

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Multiple Choice

Q 35Q 35

The SI unit of force is the
A) newton
B) gram
C) pound
D) kilogram
E) None of these is correct.

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Multiple Choice

Q 36Q 36

In the cgs system, the units of force are
A) g · cm
B) g · cm

^{2}/s^{2 }C) g · cm/s^{2 }D) g · s/cm E) cm · s^{2 }Free

Multiple Choice

Q 37Q 37

An astronaut lands on an Earthlike planet and drops a small lead ball with a mass of 76.5 g from the top of her spaceship. The point of release is 18 m above the surface of the planet and the ball takes 2.5 s to reach the ground. The astronaut's mass on Earth is 68.5 kg. Her weight on the planet is
A) 69.0 N
B) 395 N
C) 670 N
D) 990 N
E) 1.02 kN

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Multiple Choice

Q 38Q 38

A shopper steps on an escalator moving downward at a constant speed toward the bargain basement in a large department store. On his way down, the normal force exerted on him by the step of the escalator is
A) greater than his weight when he is off the escalator.
B) equal to his weight when he is off the escalator.
C) less than his weight when he is off the escalator.
D) dependent on how fast the escalator is moving.
E) unknown; insufficient information is given to answer correctly.

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Multiple Choice

Q 39Q 39

The acceleration due to gravity on the moon is only about 1/6 of that on Earth. An astronaut whose weight on Earth is 600 N travels to the lunar surface. His mass as measured on the moon is
A) 600 kg
B) 100 kg
C) 61.2 kg
D) 10.0 kg
E) 360 kg

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Multiple Choice

Q 40Q 40

Which of the following is not a unit of force?
A) newton
B) pound
C) slug
D) dyne
E) kg · m/s

^{2 }Free

Multiple Choice

Q 41Q 41

Which of the following is not a unit of mass?
A) pound
B) kilogram
C) gram
D) slug
E) milligram

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Multiple Choice

Q 42Q 42

What is the weight of a 50-kg boy on the moon, where the acceleration due to gravity is 1.6 m/s

^{2}? A) 80 N B) 100 N C) 490 N D) 50 N E) 80 lbFree

Multiple Choice

Q 43Q 43

You are going up in an elevator that is accelerating upwards on Earth. Suppose you were to do the same thing on Mars. Your weight on Mars will be ___ your weight on Earth.
A) less than
B) equal to
C) greater than
D) unable to tell
E) depends on what g is on Mars

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Multiple Choice

Q 44Q 44

The force needed to accelerate "Opportunity" (Opportunity is a Mars rover) on Mars at 1 m/s

^{2}in the horizontal direction is ____ the force needed to accelerate the rover while it was undergoing testing on Earth. A) less than B) equal to C) greater than D) unable to tell E) depends on what g is on MarsFree

Multiple Choice

Q 45Q 45

Which of the following is a unit of force?
A) m

^{2}/s^{2 }B) kg · s^{2}/m C) kg · m/s^{2 }D) N · s E) N/kgFree

Multiple Choice

Q 46Q 46

Of the following values, which is most nearly equal to the weight of a 1-kg body?
A) 1 N
B) 103 dynes
C) 2.2 lb
D) 0.454 lb
E) 2.2 N

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Multiple Choice

Q 47Q 47

The system in the figure consists of a steel ball attached by a cord to a large block of wood. If the system is dropped in a vacuum, the force in the cord is
A) zero.
B) equal to the difference of the masses of B and W.
C) equal to the difference of the weights of B and W.
D) equal to the weight of B.
E) equal to the sum of the weights of B and W.

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Multiple Choice

Q 48Q 48

A 44.5-N weight is hung on a spring scale, and the scale is hung on a string. The string is lowered at a rate such that the entire assembly has a downward acceleration of 4.90 m/s

^{2}. The scale reads A) 0 N B) 22.2 N C) 44.5 N D) 66.7 N E) 71.2 NFree

Multiple Choice

Q 49Q 49

In a crash test the strapped-in, 75-kg dummy moves a distance of 0.80 m when the test car is slammed straight into a wall at 11.2 m/s (~25 mph). The average force acting on the dummy during the collision is how many times his own weight?
A) 0.13
B) 78
C) 0.71
D) 8.0
E) 4.0

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Multiple Choice

Q 50Q 50

We all know it makes sense to bend one's knees when dropping from a height.
Suppose a very silly 70-kg person were instead to drop down from a height of 1.4 m onto the ground and stop stiffly within a distance of only 0.60 cm. Calculate how many times his own weight is the average force his body feels.
A) 15
B) 24
C) 2.3 10

^{3 }D) 6.1 10^{2 }E) 2.3 10^{2 }Free

Multiple Choice

Q 51Q 51

A book is placed on a flat horizontal table. The table exerts a normal force on the book. The origin of the normal force in terms of the fundamental forces is
A) gravitational force.
B) electromagnetic force.
C) weak nuclear force
D) strong nuclear force
E) all the four forces

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Multiple Choice

Q 52Q 52

If a force F is required to extend a spring by 20 cm, what force is required to extend it by 30 cm?
A) F
B) (2/3)F
C) (3/2)F
D) 600F
E) (3/5)F

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Multiple Choice

Q 53Q 53

If a force F is required to extend a spring a distance 5y, how far will it be extended by force 3F?
A) 5y
B) (3/5)y
C) (5/3)y
D) 15y
E) (3/8)y

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Multiple Choice

Q 54Q 54

Spiral springs A and B are identical. When a weight of 12 N is fastened to the hook on A, the hook is lowered 2 cm. If a weight of 18 N is fastened to the hook on B, that hook is lowered
A) 8 cm
B) 6 cm
C) 3 cm
D) 4 cm
E) 5 cm

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Multiple Choice

Q 55Q 55

The concept of a field
A) provides us with a way to understand how a body's presence is known over great distances.
B) is a useful alternative to action at a distance for explaining gravitational forces.
C) is that of space distorted by the presence of an object.
D) is useful in describing electromagnetic interactions as well as gravitational interactions.
E) is described by all of these.

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Multiple Choice

Q 56Q 56

Which of the following free-body diagrams represents the block sliding down a frictionless inclined plane?
A) 1
B) 2
C) 3
D) 4
E) 5

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Multiple Choice

Q 57Q 57

Which of the following free-body diagrams represents the car going uphill at a constant speed?
A) 1
B) 2
C) 3
D) 4
E) 5

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Multiple Choice

Q 58Q 58

Which of the following free-body diagrams represents the car going downhill without acceleration?
A) 1
B) 2
C) 3
D) 4
E) 5

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Multiple Choice

Q 59Q 59

A net force is exerted toward the east on an object that is initially at rest. In which direction does the object start to move?
A) north
B) east
C) west
D) south
E) It may start to move in any of these directions.

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Multiple Choice

Q 60Q 60

A horse-drawn coach is decelerating at 3.0 m/s

^{2}while moving in a straight line horizontally. A 350-g mass is hanging on a string 1.6 m long from the ceiling of the coach. The angle that the string makes with the vertical is A) 9.3º toward the front of the coach. B) 17º toward the front of the coach. C) 9.3º toward the back of the coach. D) 2.5º toward the front of the coach. E) 0º, or straight down.Free

Multiple Choice

Q 61Q 61

A car is accelerating at a rate of 2.5 m/s

^{2}. A mass of 250 g is hanging from the ceiling on a string 1.2 m long. The angle that the string makes with the vertical is A) 14.3º toward the back of the car. B) 76º toward the back of the car. C) 7º toward the front of the car. D) 14.3º toward the front of the car. E) 0º, or straight down.Free

Multiple Choice

Q 62Q 62

A lamp with a mass m = 42.6 kg is hanging from wires as shown. The tension

_{1}in the vertical wire is A) 210 N B) 417 N C) 570 N D) 360 N E) 730 NFree

Multiple Choice

Q 63Q 63

A lamp with a mass m is suspended from the ceiling by two cords as shown. The ratio of the magnitude of the vertical component of the tension in

_{2}to that in_{3}is A) 1:1 B) 1:2 C) D) 3:2 E) 3:1Free

Multiple Choice

Q 64Q 64

A boy sits in a tire that is attached to a rope that passes over a pulley fastened to the ceiling and then passes back down to the boy's hands. The weight of the boy plus the tire is W. The force with which the boy must pull on the free end of the rope to support his weight in the tire is
A) (1/2)W
B) W
C) 2W
D) (2/3)W
E) (3/2)W

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Multiple Choice

Q 65Q 65

A vertical rope is attached to an object that has a mass of 40.0 kg and is at rest. The tension in the rope needed to give the object an upward speed of 3.50 m/s in 0.700 s is
A) 592 N
B) 390 N
C) 200 N
D) 980 N
E) 720 N

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Multiple Choice

Q 66Q 66

A particle of mass 1.3 kg is sliding down a frictionless slope inclined at 30º to the horizontal. The acceleration of the particle down the slope is
A) 1.3 m/s

^{2 }B) 9.8 m/s^{2 }C) 0.5 m/s^{2 }D) 8.5 m/s^{2 }E) 4.9 m/s^{2 }Free

Multiple Choice

Q 67Q 67

You want to elope by sliding down a nylon rope made by tying stockings together. The rope will withstand a maximum tension of 300 N without breaking. Your mass is 61.2 kg. The magnitude of the smallest acceleration a with which you can slide down the rope is
A) 9.81 m/s

^{2 }B) 4.91 m/s^{2 }C) zero D) 2.40 m/s^{2 }E) 19.6 m/s^{2 }Free

Multiple Choice

Q 68Q 68

Three forces, , , and , act on a mass of 4.2 kg. The forces are = 2.0 N acting to the east, = 5.0 N acting 45º to the north of east, and = 4.0 N acting 30º to the north of west.
The magnitude of the net acceleration of the mass is
A) 2.9 m/s

^{2 }B) 5.3 m/s^{2 }C) 1.4 m/s^{2 }D) 0.0 m/s^{2 }E) 18 m/s^{2 }Free

Multiple Choice

Q 69Q 69

Three forces, , , and , act on a mass of 4.2 kg. The forces are = 2.0 N acting to the east, = 5.0 N acting 45º to the north of east, and = 4.0 N acting 30º to the north of west.
The direction of the net acceleration
A) cannot be determined because the acceleration is zero.
B) is 60º north of east.
C) is 70º north of east.
D) is 51º north of east.
E) is 44º north of east.

Free

Multiple Choice

Q 70Q 70

Your heart pumps 80 g of blood with each beat. The blood starts from rest and reaches a speed of 0.60 m/s in the aorta. If each beat takes 0.16 s, the average force exerted on the blood is
A) 3.0 10

^{2}N B) 0.22 N C) 0.16 N D) 0.30 N E) 0.98 NFree

Multiple Choice

Q 71Q 71

A man riding in an elevator has an apparent weight greater than his actual weight. Which one of the following statements could be true?
A) The elevator moves upward with constant speed.
B) The elevator moves downward with constant speed.
C) The elevator moves upward with decreasing speed.
D) The elevator moves downward with decreasing speed.
E) The elevator moves downward with increasing speed.

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Multiple Choice

Q 72Q 72

A bell hangs from a blue rope. A red rope attached to the side of the bell is pulled in the horizontal direction. This causes the blue rope to make an angle less than 90º with the vertical. Which of the following statements is true?
A) The red rope is under greater tension than the blue rope.
B) The red rope is under the same tension as the blue rope.
C) The blue rope is under greater tension than the red rope.
D) The tensions cannot be compared unless the mass of the bell is known.
E) The tensions cannot be compared unless the angle that the blue rope makes with the vertical is known.

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Multiple Choice

Q 73Q 73

A net force is exerted on an object toward the north. The object
A) is moving toward the north.
B) is moving toward the east.
C) is moving toward the west.
D) is moving toward the south.
E) may be moving in any direction.

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Multiple Choice

Q 74Q 74

A box sits on an inclined plane without sliding. As the angle of inclination increases, the normal force
A) increases.
B) decreases.
C) does not change.
D) is directed upward.
E) is directed in the direction of the gravitational force.

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Multiple Choice

Q 75Q 75

The word "normal," as it applies to forces, means
A) usual.
B) mean.
C) average.
D) perpendicular.
E) straight up, in the direction opposite to the force of gravity.

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Multiple Choice

Q 76Q 76

A lamp of mass m hangs from a spring scale that is attached to the ceiling of an elevator. When the elevator is stopped at the fortieth floor, the scale reads mg. What does it read while the elevator descends toward the ground floor at a constant speed?
A) more than mg
B) less than mg
C) mg
D) zero
E) This cannot be answered without knowing how fast the elevator is descending.

Free

Multiple Choice

Q 77Q 77

A particle has a mass of 6.0 10

^{-6}kg and a velocity of 800 m/s along the x axis when a force of 14.4 10^{-5}N along the y axis acts on the particle at right angles to its velocity. The acceleration of the particle is A) 24 m/s^{2}along the x axis. B) zero. C) impossible to determine; forces never act at right angles to velocities. D) 24 m/s^{2}along the y axis. E) tangential.Free

Multiple Choice

Q 78Q 78

A force of 3.0 N acts on a body along a direction 30º above the horizontal. In addition, there is a gravitational force of 4.0 N downward. The resultant force has a magnitude of
A) 7.0 N
B) 6.8 N
C) 6.1 N
D) 3.6 N
E) 5.0 N

Free

Multiple Choice

Q 79Q 79

A lamp of mass m hangs from a spring scale which is attached to the ceiling of an elevator. When the elevator is stopped at the fortieth floor, the scale reads mg. What does it read as the elevator slows down to stop at the ground floor?
A) more than mg
B) less than mg
C) mg
D) zero
E) One cannot tell without knowing how fast the elevator is stopping.

Free

Multiple Choice

Q 80Q 80

A lamp of mass m hangs from a spring scale that is attached to the ceiling of an elevator. When the elevator is stopped at the fortieth floor, the scale reads mg. What does it read as the elevator slows down to stop at the forty-fifth floor?
A) more than mg
B) less than mg
C) mg
D) zero
E) One cannot tell without knowing how fast the elevator is stopping.

Free

Multiple Choice

Q 81Q 81

The tension of the right-hand string divided by the tension of the left-hand string is given by
A) sin

_{2}/ sin _{1 }B) cos _{1}/ cos _{2 }C) cos _{2 }/ cos _{1 }D) sin _{1}/ sin _{2 }E) (mg T_{1}sin _{1}) / (T_{1} sin _{2})Free

Multiple Choice

Q 82Q 82

The tension in the left-hand string in terms of

_{1}, _{2}, and m is A) mg cos _{1}/ (sin _{1}sin _{2}+ cos _{1}cos _{2 }) B) mg sin _{2}/ (sin _{1}sin _{2}+ cos _{1}cos _{2 }) C) mg cos _{2}/ (sin _{1}sin _{2}+ cos _{1}cos _{2 }) D) mg cos _{2}/ (sin _{1}cos _{2}+ cos _{1}sin _{2 }) E) mg cos _{2}/ (sin _{1}cos _{2}+ cos _{1}sin _{2 })Free

Multiple Choice

Q 83Q 83

Three forces F

_{1}, F_{2}and F_{3 }act on an object. If F_{1}= 3N i + 5N j + 7N k, F_{2}= 5N i 2N j 2N k, and the object is moving at constant velocity then the vector force F_{3}is A) 2N i 3N j 5N k B) 2N i 3N j 5N k C) 2N i + 3N j 5N k D) 8N i 7N j 9N k E) 8N i + 7 N j +9N kFree

Multiple Choice

Q 84Q 84

An 80-kg man on ice skates pushes a 40-kg boy, also on skates, with a force of 100 N. The force exerted by the boy on the man is
A) 200 N
B) 100 N
C) 50 N
D) 40 N
E) zero unless the boy pushes back

Free

Multiple Choice

Q 85Q 85

A boy holds a bird in his hand. The reaction force to the normal force exerted on the bird by the boy's hand is the force of:
A) the Earth on the bird.
B) the bird on the Earth.
C) the hand on the bird.
D) the bird on the hand.
E) the Earth on the hand.

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Multiple Choice

Q 86Q 86

A boy holds a bird in his hand. The reaction force to the weight of the bird is the force of the:
A) Earth on the bird.
B) bird on the Earth.
C) hand on the bird.
D) bird on the hand.
E) Earth on the hand.

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Multiple Choice

Q 87Q 87

A body of weight w is in free fall near the surface of Earth. What force does the body exert on the Earth?
A) w
B) greater than w
C) less than w
D) 9.81w
E) zero

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Multiple Choice

Q 88Q 88

A body of weight w rests on the surface of Earth. What force does the body exert on Earth? (ignore Earth's rotation)
A) w
B) greater than w
C) less than w
D) 9.81w
E) zero

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Multiple Choice

Q 89Q 89

A girl walks on a level floor in a straight line in the +x direction. Her foot exerts a force on the floor. The direction of the reaction force by the floor on her foot is in
A) +x direction
B) -x direction
C) +y direction (vertically up)
D) -y direction (vertically down)
E) depends how fast she is walking

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Multiple Choice

Q 90Q 90

Two springs with different spring constants, k

_{1}and k_{2}, are connected as shown in the figure below. A force F is applied to one end. The force exerted by the wall on the spring is (take + to the right) A) 0 B) -k_{1}x_{1}C) -k_{2}x_{2}D) F E) -FFree

Multiple Choice

Q 91Q 91

A horse exerts a force F on a cart, causing the cart to move with increasing speed. What force does the cart exert on the horse?
A) zero
B) F
C) greater than F
D) less than F
E) The force cannot be determined unless the acceleration is given.

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Multiple Choice

Q 92Q 92

A cricket batsman hits a ball with a bat. If the force with which the bat hits the ball is considered the action force, what is the reaction force?
A) the force the bat exerts on the batsman's hands
B) the force on the ball exerted by the hand of the person who catches it
C) the force the ball exerts on the bat
D) the force the bowler exerts on the ball in throwing it
E) friction as the ball rolls to a stop

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Multiple Choice

Q 93Q 93

A man pushes horizontally on the book with force and moves it at constant speed along the table. Three "agents" exert forces on the book, shown as , , and in the second diagram, and three "agents" exert forces on the table, shown as , , and in the third diagram. The "action-reaction" forces of Newton's third law are
A) and .
B) and .
C) and .
D) and .
E) and .

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Multiple Choice

Q 94Q 94

A horse harnessed to a wagon refuses to pull, citing Newton's third law, which states that for every force there is an equal but opposite reaction force. The horse, incorrect in its reasoning, can pull the wagon because
A) after it gives a jerk and the wagon is moving, its pulling force will be greater than the reaction to this force.
B) the law applies only to static cases.
C) the wagon cannot possibly pull back with a force equal in magnitude to the pulling force.
D) the action and reaction forces are acting on different bodies.
E) after friction is overcome, the reaction force is less than the pulling force.

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Multiple Choice

Q 95Q 95

Two masses, m

_{1}and m_{2}, connected by a massless string, are accelerated uniformly on a frictionless surface as shown. The ratio of the tensions_{1}/_{2}is given by A) m_{1}/m_{2 }B) m_{2}/m_{1 }C) (m_{1}+ m_{2})/m_{2 }D) m_{1}/(m_{1}+ m_{2}) E) m_{2}/(m_{1}+ m_{2})Free

Multiple Choice

Q 96Q 96

A mass 2m is attached by a string to another mass m as illustrated. A force of newtons acts on mass m to accelerate the system. The force in the string, which acts on mass 2m, is
A) (2/3)N
B) N
C) 2N
D) 3N
E) (3/2)N

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Multiple Choice

Q 97Q 97

You are riding an elevator that is accelerating upward at 2.20 m/s

^{2}. You have a spring balance accurately calibrated in newtons. When you hang a mass of 10.0 kg on the balance, the reading of the balance is A) 120 N B) 981 N C) 76.0 N D) 10.0 N E) 9.81 NFree

Multiple Choice

Q 98Q 98

An object with a mass M = 250 g is on a plane inclined at 30º above the horizontal and is attached by a string to a mass m = 150 g. There is no friction and mass m hangs freely and is initially at rest. When mass m has descended a distance h = 10 cm, its speed will be
A) 35.0 cm/s
B) 7.00 cm/s
C) 140 cm/s
D) 110 cm/s
E) 70.0 cm/s

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Multiple Choice

Q 99Q 99

A mass m is hanging on a string that passes over a pulley and is then attached to another mass 3m that is resting on a horizontal table. Neglect friction. Mass m is held motionless and is then released. When it has fallen a distance h, it will have a speed v which can be calculated from the formula
A)
B)
C)
D)
E) None of these is correct.

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Multiple Choice

Q 100Q 100

If two metal blocks of different masses slide freely down the same frictionless incline, which one of the following is true?
A) They have equal accelerations
B) They have unequal accelerations, but the forces acting on them are equal.
C) The more massive block reaches the bottom first.
D) The less massive block reaches the bottom first.
E) None of these is correct.

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Multiple Choice

Q 101Q 101

A 15-kg block sitting on a smooth table is connected to a free-hanging 5-kg mass by a stretchless, massless cord that passes over a small frictionless pulley. The acceleration of the two-block system is
A) equal to g.
B) half of g.
C) one-third of g.
D) one-fourth of g.
E) zero.

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Multiple Choice

Q 102Q 102

A 6-kg block sitting on a smooth table is connected to a free-hanging 2-kg mass by a stretchless, massless cord that passes over a small frictionless pulley. The acceleration of the two-block system is
A) equal to g.
B) half of g.
C) one-third of g.
D) one-fourth of g.
E) two-thirds of g.

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Multiple Choice

Q 103Q 103

For this problem, assume no friction. A mass m

_{2}= 3.5 kg rests on a horizontal table and is attached by strings to masses m_{1 }= 1.5 kg and m_{3 }= 2.5 kg as shown. The masses m_{1}and m_{3}hang freely. The system is initially held at rest. After it is released, the acceleration of mass m_{2}will be A) zero B) 1.3 m/s^{2 }C) 5.2 m/s^{2 }D) 8.7 m/s^{2 }E) 9.8 m/s^{2 }Free

Multiple Choice

Q 104Q 104

Three boxes are connected by stretchless strings and are pulled by a force as shown in the figure. Which string has to be the strongest so as not to break?
A) A
B) B
C) C
D) A, B, and C must be equally strong.
E) A and B must be equally strong.

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Multiple Choice

Q 105Q 105

Three boxes are connected by stretchless strings and are pulled by a force as shown in the figure. Which box has the greatest acceleration?
A) A
B) B
C) C
D) they all have the same acceleration
E) the accelerations of B and C are greater than that of A

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Multiple Choice

Q 106Q 106

Two tug-of-war teams are pulling on the ends of a rope, each team with a force of 1000 N. If the rope does not move, the tension in the rope is
A) 2000 N
B) 500 N
C) 1000 N
D) 0 N
E) 2000 kg

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Multiple Choice

Q 107Q 107

Two groups of five men each are engaged in a tug-of-war, each man pulling with a force of 900 N. If the rope does not move, the tension in it is
A) 18 kN
B) 9.0 kN
C) 44 kN
D) 4.5 kN
E) 0.46 kN

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Multiple Choice

Q 108Q 108

Two boxes m

_{1}and m_{2}are connected by a lightweight cord and sitting on a frictionless surface. A horizontal force of 66 N pulls on box m_{1}and then m_{2}is pulled along. If the acceleration of both boxes is 2.2 m/s^{2}and the mass of m_{1}is 12 kg, find the mass of m_{2}. A) 12 kg B) 18 kg C) 30 kg D) 48 kg E) 42 kgFree

Multiple Choice

Q 109Q 109

A force of F = 90 N is exerted on mass m

_{1}as shown. Both m_{1}and m_{2}accelerate to the right at 3 m/s along the frictionless surface. The force F makes an angle of 25 degrees to the horizontal. If m_{2}= 10 kg, calculate the mass m_{1}. A) 2.7 kg B) 17 kg C) 27 kg D) 1.8 kg E) 24 kgFree

Multiple Choice

Q 110Q 110

A force of F = 90 N is exerted on mass m

_{1}as shown. Both m_{1}and m_{2}accelerate to the right at 3 m/s^{2}along the frictionless surface. The force F makes an angle of 25 degrees to the horizontal. Calculate the force that the horizontal surface exerts on mass m_{1}. (m_{2}= 10 kg) A) 2.5 10^{2}N B) 1.5 10^{2}N C) 82 N D) 3.5 10^{2}N E) 2.1 10^{2}NFree

Multiple Choice

Q 111Q 111

Two masses m

_{1}and m_{2}(with m_{2}> m_{1}) are connected by a massless rope hung over a frictionless light pulley. If the masses are released then the acceleration of m_{2}in the downward direction is given by A) (m_{2} m_{1}) g/(m_{1} m_{2}) B) (m_{2} m_{1}) g/(m_{1}+ m_{2}) C) (m_{1}+ m_{2}) g/(m_{2} m_{1}) D) m_{2} g/(m_{1}+ m_{2}) E) gFree

Multiple Choice

Q 112Q 112

Two masses m

_{1}= 12 kg and m_{2}= 35 kg are held connected by a massless rope hung over a frictionless light pulley. If the masses are released then the magnitude of the tension in the string is A) 343 N B) 58.0 N C) 226 N D) 458 N E) 175 NFree

Multiple Choice

Q 113Q 113

A frictionless pulley of negligible mass is hung from the ceiling using a rope, also of negligible mass. Two masses, m

_{1}and m_{2}(m_{1}< m_{2}) are connected to the rope over the pulley. The masses are free to drop. The magnitude of the tension T_{top}is ____ the sum of the tensions T_{1}and T_{2}. A) less than B) equal to C) greater than D) unable to tell E) depends on T_{top}Free

Multiple Choice

Q 114Q 114

A frictionless pulley of negligible mass is hung from the ceiling using a rope, also of negligible mass. Two masses, m

_{1}and m_{2}(m_{1}< m_{2}) are connected to the rope over the pulley. The masses are free to drop. The magnitude of the tension T_{top}is ____ the sum of the weights W_{1}= m_{1}g and W_{2}_{ }= m_{2}g. A) less than B) equal to C) greater than D) unable to tell E) depends on T_{1}and T_{2}.Free

Multiple Choice

Q 115Q 115

A large (15,000-kg) military helicopter lifts a 6000-kg truck straight up out of a danger zone with an acceleration of 4 m/s

^{2}. Calculate the tension in the lifting cable. A) 3.5 10^{4}N B) 8.3 10^{4}N C) 2.1 10^{2}N D) 5.9 10^{4}N E) 2.4 10^{4}NFree

Multiple Choice

Q 116Q 116

Three blocks are connected by massless cords and rest on a frictionless horizontal surface. The blocks are pulled to the right. Mass m

_{1}= 2 m_{2}= 3 m_{3}, with m_{1}on the left and m_{3}on the right. If the pulling force is equal to 90 N, then the tension in the cord between m_{1}and m_{2}is A) 49 N B) 15 N C) 100 N D) 44 N E) 85 NFree

Multiple Choice

Q 117Q 117

Three blocks are connected by massless cords and hung by a third massless cord to a beam. Mass m

_{1}= 2 m_{2}= 3 m_{3}. Mass m_{1}is the lowest block and m_{3}is the highest. The tension in the cord between the two highest blocks is A) 3m_{1} g/2 B) m_{1} g/2 C) m_{1} g/6 D) 2m_{1} g/3 E) 6m_{1} g/11Free

Multiple Choice