Question 1

You jump off an airplane and fall freely for a while (before you open a parachute). Which of these statements describes what is happening in this situation?

Accepted Answer

B

Question 2

Figure 4.1
​ 
-When a scale is pulled by two identical forces, 10 N each, as in Fig. 4.1, what will the scale read?

Accepted Answer

The scale reads the tension in the rope, which is the force exerted by one side. Since both forces are equal and opposite, the scale reads 10 N.

Question 3

A seal is sunbathing on an inclined rock, and NOT slipping. Which one of these statements correctly describes the normal force?

Accepted Answer

The normal force is the component of the seal's weight perpendicular to the surface of the inclined rock. Since the rock is inclined, not all of the seal's weight acts perpendicular to the surface; some of it acts parallel to the surface. Therefore, the normal force is smaller than the total weight of the seal.

Question 4

Two flying squirrels of roughly the same size but with different masses, m₁ = 110 g and m₂ = 180 g, fly from a high tree. What is the ratio of terminal velocities v₁ and v₂ for the two squirrels?

Accepted Answer

The terminal velocity of a falling object is proportional to the square root of its mass. Therefore, the ratio of terminal velocities is:v₁ / v₂ = √(m₁ / m₂) = √(110 g / 180 g) = 0.78

Question 5

A child holds a ball in her hand. Which of these forces is opposite but equal in magnitude to the weight of the ball?

Accepted Answer

The answer of A child holds a ball in her...

Question 6

The coefficient of static friction between a seal and a steep rock is 0.8. What is the steepest incline angle of a rock that the seal can lie on without slipping?

Accepted Answer

The answer of The coefficient of static friction between a...

Question 7

Figure 4.3 The figure shows two objects of masses mS1U1B11S1U1B0 and mS1U1B12S1U1B0, placed on two inclined surfaces of different angles èS1U1B11S1U1B0 and èS1U1B12S1U1B0. The connection between masses is a taut, massless string running over a massless and frictionless pulley. -In Fig. 4.3, the two masses are the same (m₁ = m₂ = 10 kg); the incline angles are è₁ = 30° and è₂ = 50°. What are the magnitude and direction of the acceleration of the system, and the tension in the string, if both inclined surfaces are frictionless?

Accepted Answer

The answer of Figure 4.3  The figure shows two...

Question 8

You charge a balloon by rubbing it on your hair and it sticks to the ceiling by electrostatic force. Which of these four free body diagrams describes all the forces acting on the balloon? The forces are labelled as follow:  is the weight of the balloon,  is electrostatic force, and  is a normal force.

Accepted Answer

The answer of You charge a balloon by rubbing it...

Question 9

Figure 4.2  Two crates connected by a string passed through a pulley.
-Two weights, one with mass 2 kg and the other with mass 4 kg, are attached to the ends of a massless string that hangs over an ideal pulley. The system is allowed to move freely. What is the value of acceleration of the system?

Accepted Answer

The acceleration of the system can be calculated using the formula $a = \frac{g(m_2 - m_1)}{m_1 + m_2}$, where $m_1$ and $m_2$ are the masses and $g$ is the acceleration due to gravity (9.8 m/s$^2$). Substituting $m_1 = 2$ kg, $m_2 = 4$ kg, and $g = 9.8$ m/s$^2$, we get $a = \frac{9.8(4 - 2)}{2 + 4} = 3.3$ m/s$^2$.

Question 10

Figure 4.3 The figure shows two objects of masses mS1U1B11S1U1B0 and mS1U1B12S1U1B0, placed on two inclined surfaces of different angles èS1U1B11S1U1B0 and èS1U1B12S1U1B0. The connection between masses is a taut, massless string running over a massless and frictionless pulley. -In Fig. 4.3, masses are m₁= 10 kg and m₂ = 15 kg; incline angle is è₁ = 30°. What is the value of è₂ if the system is NOT moving?

Accepted Answer

The answer of Figure 4.3  The figure shows two...

Question 11

You are moving in an elevator with constant speed, on the way up. Which of these statements correctly describes the normal force exerted by the floor of the elevator on you?

Accepted Answer

When the elevator moves with constant speed (up or down), there is no acceleration in the vertical direction. Therefore, the normal force exerted by the floor of the elevator on you equals your weight, just as it would if you were standing still off the elevator.

Question 12

Figure 4.3 The figure shows two objects of masses mS1U1B11S1U1B0 and mS1U1B12S1U1B0, placed on two inclined surfaces of different angles èS1U1B11S1U1B0 and èS1U1B12S1U1B0. The connection between masses is a taut, massless string running over a massless and frictionless pulley. -In Fig. 4.3, mass m₁= 5 kg and incline angles are è₁ = 30° and è₂ = 50°. Both inclines are smooth frictionless surfaces. What is the value of m₂ if the system is NOT moving?

Accepted Answer

The answer of Figure 4.3  The figure shows two...

Question 13

A sled is gliding down an incline with angleè. In the absence of friction, what component of the weight is driving the sled downward?

Accepted Answer

The component of the weight driving the sled downward on an incline is mgsinè, where mg is the gravitational force acting on the sled and è is the angle of the incline. This component is perpendicular to the surface of the incline.

Question 14

Figure 4.4  The figure shows two bodies of masses M and m, M placed on a horizontal surface and m hanging at the side, connected by a light cord over a massless and frictionless pulley.
-In Fig. 4.4, the masses are M = 3 kg and m = 5 kg. What is the minimum coefficient of static friction between the horizontal surface and M such that the system is NOT moving?

Accepted Answer

The answer of Figure 4.4  The figure shows two...

Question 15

You exercise with a 5.0 kg dumbbell. You need to accelerate it downward with an acceleration of 3.0 m/s². What are the magnitude and the direction of the force you need to push with?

Accepted Answer

To find the force needed, use Newton's second law: F = ma. The weight of the dumbbell is 49 N (5.0 kg * 9.8 m/s²). To accelerate it downward at 3.0 m/s², the net force should be 15 N downward (5.0 kg * 3.0 m/s²). Therefore, you need to apply a force of 24 N upward to achieve this net force (49 N - 24 N = 15 N downward).

Question 16

A truck has a crate in its cargo bed. If the truck accelerates forward and the crate does NOT move, in which of these directions is the frictional force that the floor of the cargo bed exerts on the crate?

Accepted Answer

The frictional force must act in the forward direction to prevent the crate from sliding backward due to the truck's acceleration. This force is what keeps the crate stationary relative to the truck.

Question 17

If an object is falling freely, what is the gravitational force equal to?

Accepted Answer

The gravitational force on a freely falling object is equal to the object's weight, which is the force of gravity acting on the object's mass.

Question 18

Figure 4.4  The figure shows two bodies of masses M and m, M placed on a horizontal surface and m hanging at the side, connected by a light cord over a massless and frictionless pulley.
-In Fig. 4.4, the masses are M = 10 kg and m = 20 kg. The coefficient of friction for the horizontal surface is ì = 0.4. What are the acceleration of the system and the tension in the string?

Accepted Answer

The acceleration of the system can be calculated using Newton's second law and considering the forces acting on both masses, including the force of gravity, tension, and friction. The tension in the string is determined by the force needed to accelerate both masses. Given the coefficient of friction and the masses, the correct calculations lead to an acceleration of 5.2 m/s^2 and a tension of 92 N.

Question 19

Which of the following statements include all the essential elements of Newton's first law?

Accepted Answer

Newton's first law, also known as the law of inertia, states that an object will remain at rest or in uniform motion in a straight line unless acted upon by a non-zero net external force. This is accurately reflected in option D.

Question 20

A student in an elevator is checking Newton's laws using a scale. The scale is showing a reading lower than the student's actual weight. Which one of these statements explains this phenomenon?

Accepted Answer

When the elevator moves upward with decreasing speed, it is decelerating, which means there is a net downward acceleration. This causes the normal force (scale reading) to be less than the gravitational force (actual weight).

Quiz 4: Newtons Laws

You jump off an airplane and fall freely for a while (before you open a parachute) . Which of these statements describes what is happening in this situation?

Figure 4.1 -When a scale is pulled by two identical forces, 10 N each, as in Fig. 4.1, what will the scale read?

A seal is sunbathing on an inclined rock, and NOT slipping. Which one of these statements correctly describes the normal force?

Two flying squirrels of roughly the same size but with different masses, m₁ = 110 g and m₂ = 180 g, fly from a high tree. What is the ratio of terminal velocities v₁ and v₂ for the two squirrels?

A child holds a ball in her hand. Which of these forces is opposite but equal in magnitude to the weight of the ball?

The coefficient of static friction between a seal and a steep rock is 0.8. What is the steepest incline angle of a rock that the seal can lie on without slipping?

You charge a balloon by rubbing it on your hair and it sticks to the ceiling by electrostatic force. Which of these four free body diagrams describes all the forces acting on the balloon? The forces are labelled as follow: is the weight of the balloon, is electrostatic force, and is a normal force.

Figure 4.2 Two crates connected by a string passed through a pulley. -Two weights, one with mass 2 kg and the other with mass 4 kg, are attached to the ends of a massless string that hangs over an ideal pulley. The system is allowed to move freely. What is the value of acceleration of the system?

You are moving in an elevator with constant speed, on the way up. Which of these statements correctly describes the normal force exerted by the floor of the elevator on you?

A sled is gliding down an incline with angleè. In the absence of friction, what component of the weight is driving the sled downward?

You exercise with a 5.0 kg dumbbell. You need to accelerate it downward with an acceleration of 3.0 m/s². What are the magnitude and the direction of the force you need to push with?

A truck has a crate in its cargo bed. If the truck accelerates forward and the crate does NOT move, in which of these directions is the frictional force that the floor of the cargo bed exerts on the crate?

If an object is falling freely, what is the gravitational force equal to?

Which of the following statements include all the essential elements of Newton's first law?

A student in an elevator is checking Newton's laws using a scale. The scale is showing a reading lower than the student's actual weight. Which one of these statements explains this phenomenon?

Quiz 4: Newtons Laws

You jump off an airplane and fall freely for a while (before you open a parachute) . Which of these statements describes what is happening in this situation?

Figure 4.1 ​ -When a scale is pulled by two identical forces, 10 N each, as in Fig. 4.1, what will the scale read?

A seal is sunbathing on an inclined rock, and NOT slipping. Which one of these statements correctly describes the normal force?

Two flying squirrels of roughly the same size but with different masses, m1 = 110 g and m2 = 180 g, fly from a high tree. What is the ratio of terminal velocities v1 and v2 for the two squirrels?

A child holds a ball in her hand. Which of these forces is opposite but equal in magnitude to the weight of the ball?

The coefficient of static friction between a seal and a steep rock is 0.8. What is the steepest incline angle of a rock that the seal can lie on without slipping?

You charge a balloon by rubbing it on your hair and it sticks to the ceiling by electrostatic force. Which of these four free body diagrams describes all the forces acting on the balloon? The forces are labelled as follow: is the weight of the balloon, is electrostatic force, and is a normal force.

Figure 4.2 Two crates connected by a string passed through a pulley. -Two weights, one with mass 2 kg and the other with mass 4 kg, are attached to the ends of a massless string that hangs over an ideal pulley. The system is allowed to move freely. What is the value of acceleration of the system?

You are moving in an elevator with constant speed, on the way up. Which of these statements correctly describes the normal force exerted by the floor of the elevator on you?

A sled is gliding down an incline with angleè. In the absence of friction, what component of the weight is driving the sled downward?

You exercise with a 5.0 kg dumbbell. You need to accelerate it downward with an acceleration of 3.0 m/s2. What are the magnitude and the direction of the force you need to push with?

A truck has a crate in its cargo bed. If the truck accelerates forward and the crate does NOT move, in which of these directions is the frictional force that the floor of the cargo bed exerts on the crate?

If an object is falling freely, what is the gravitational force equal to?

Which of the following statements include all the essential elements of Newton's first law?

A student in an elevator is checking Newton's laws using a scale. The scale is showing a reading lower than the student's actual weight. Which one of these statements explains this phenomenon?

Figure 4.1 -When a scale is pulled by two identical forces, 10 N each, as in Fig. 4.1, what will the scale read?

Two flying squirrels of roughly the same size but with different masses, m₁ = 110 g and m₂ = 180 g, fly from a high tree. What is the ratio of terminal velocities v₁ and v₂ for the two squirrels?

You exercise with a 5.0 kg dumbbell. You need to accelerate it downward with an acceleration of 3.0 m/s². What are the magnitude and the direction of the force you need to push with?