Question 1

A block of mass m is at rest on an inclined plane that makes an angle of 30º with the horizontal,as shown in the figure.Which of the following statements about the force of static friction is true?

Accepted Answer

D

Question 2

A worker pulls horizontally on a rope that is attached to a 10-kg crate resting on a rough floor.The coefficients of static and kinetic friction are 0.5 and 0.3,respectively.The worker pulls with a force of 40 N.The frictional force exerted by the surface is

Accepted Answer

E

Question 3

Two objects are sliding at the same speed across a wooden surface.The coefficient of kinetic friction between the first object and the surface is twice that between the second object and the surface.The distance traveled by the first object before it stops is S.The distance traveled by the second object is

Accepted Answer

The distance traveled before stopping due to friction is inversely proportional to the coefficient of kinetic friction. If the coefficient for the first object is twice that of the second, the second object will travel twice the distance before stopping, making the correct answer 2S.

Question 4

A mass m is placed on a rough incline at an angle $\theta$ to the horizon.A force F is applied up the incline,to prevent the mass from sliding down the incline,and it is just enough to prevent the mass from sliding down the incline.Using the compass rose,the direction of the frictional force is along

Accepted Answer

The direction of the frictional force is always opposite to the direction of motion or impending motion. Since the applied force F is up the incline, the direction of motion or impending motion is down the incline. Therefore, the frictional force must act in the direction opposite to the applied force, which is down the incline. Choice B) shows the frictional force acting in this direction.

Question 5

A tired worker pushes a heavy (100-kg)crate that is resting on a thick pile carpet.The coefficients of static and kinetic friction are 0.6 and 0.4,respectively.The worker pushes with a force of 500 N.The frictional force exerted by the surface is

Accepted Answer

The frictional force is equal to the coefficient of friction times the normal force. The normal force is equal to the weight of the crate, which is 100 kg * 9.8 m/s^2 = 980 N. Therefore, the frictional force is 0.4 * 980 N = 392 N.

Question 6

A block of wood is pulled by a horizontal string across a rough surface at a constant velocity with a force of 20 N.The coefficient of kinetic friction between the surfaces is 0.3.The force of friction is

Accepted Answer

Since the block moves at a constant velocity, the force of friction must equal the pulling force, which is 20 N, to satisfy Newton's first law of motion.

Question 7

An object with a mass of 5.5 kg is allowed to slide from rest down an inclined plane.The plane makes an angle of 30º with the horizontal and is 72 m long.The coefficient of friction between the plane and the object is 0.35.The speed of the object at the bottom of the plane is

Accepted Answer

The speed can be found using energy conservation. The gravitational potential energy lost is converted into kinetic energy and work done against friction. Calculate the gravitational force component along the plane, subtract the frictional force, and use the work-energy principle to find the final speed.

Question 8

A mass M = 5.6 kg on a horizontal table is pulled by a horizontal string that passes over a frictionless pulley to a free-hanging mass m = 3.4 kg.The coefficient of friction between M and the table is 0.28.The acceleration of M is

Accepted Answer

To find the acceleration, we first calculate the net force acting on the system. The force due to gravity on the hanging mass (m) is $F_g = m \cdot g = 3.4 \, \text{kg} \cdot 9.8 \, \text{m/s}^2 = 33.32 \, \text{N}$. The frictional force opposing the motion on mass M is $F_{\text{friction}} = \mu \cdot N = \mu \cdot M \cdot g = 0.28 \cdot 5.6 \, \text{kg} \cdot 9.8 \, \text{m/s}^2 = 15.3472 \, \text{N}$. The net force is then $F_{\text{net}} = F_g - F_{\text{friction}} = 33.32 \, \text{N} - 15.3472 \, \text{N} = 17.9728 \, \text{N}$. The total mass of the system is $M + m = 5.6 \, \text{kg} + 3.4 \, \text{kg} = 9 \, \text{kg}$. The acceleration is $a = \frac{F_{\text{net}}}{M + m} = \frac{17.9728 \, \text{N}}{9 \, \text{kg}} = 1.997 \, \text{m/s}^2$, which rounds to $2.0 \, \text{m/s}^2$.

Question 9

A heavy truck and a light car are traveling at the same speed on the same roadway.If the coefficients of static friction between their tires and the road are the same,which vehicle will be able to stop in the shortest distance? Assume both have the same braking force.

Accepted Answer

Since both vehicles are traveling at the same speed and have the same coefficient of static friction, they will both be able to stop in the same distance. The mass of the vehicles does not affect the stopping distance in this case, as both have the same braking force. The coefficient of kinetic friction is not relevant since the question only asks about stopping distance, not the motion of the vehicles after braking.

Question 10

Which of the following statements is NOT true about friction?

Accepted Answer

The force of static friction does not depend on the area of contact between the two surfaces; it depends on the normal force and the materials in contact, represented by the coefficient of static friction.

Question 11

An Atomic Force Microscope consists of a cantilever with a very fine tip on one end.The lever is driven by a piezoelectric motor allowing the tip to scan a surface on an atomic scale.As it scans the surface what is the main frictional force between the tip and the surface?

Accepted Answer

The main frictional force between the tip of an Atomic Force Microscope (AFM) and the surface it scans is kinetic friction. This is because the tip is in motion relative to the surface, leading to resistance that is characterized as kinetic friction. Static friction would be relevant if the tip were not moving relative to the surface, and rolling friction is not applicable since the tip does not roll over the surface but rather scans across it.

Question 12

Which fundamental force(s)gives rise to friction?

Accepted Answer

Friction is a force generated by the interaction between two surfaces in contact with each other. This interaction is a result of the electromagnetic force between atoms in the two surfaces. Therefore, the fundamental force giving rise to friction is the electromagnetic force (B).

Question 13

A mass m is placed on a rough incline at an angle $\theta$ to the horizon.A force F is applied up the incline so that the mass slides up the incline.Using the compass rose,the direction of the frictional force is along

Accepted Answer

The frictional force always acts in the opposite direction of the motion or the tendency of the motion. In this case, the force applied is up the incline, and the mass slides up the incline, so the tendency of motion is down the incline. Therefore, the direction of the frictional force is along choice (d), opposite to the direction of motion.

Question 14

A 100-kg block is pushed up a 30º incline that is 10 m long.If the coefficient of friction between the block and the incline is 0.1,the constant force parallel to the incline that is required to move the block from rest at the bottom of the incline to the top in 3 s is approximately

Accepted Answer

The answer of A 100-kg block is pushed up a...

Question 15

An object with a mass M = 250 g is at rest on a plane that makes an angle $\theta$ = 30º above the horizontal.The coefficient of kinetic friction between M and the plane is µ_k = 0.100.Mass M is attached by a string to another mass, m = 200 g,which hangs freely.When mass m has fallen 30.0 cm,its speed is

Accepted Answer

The answer of An object with a mass M =...

Question 16

The SI units for the coefficient of friction are

Accepted Answer

The coefficient of friction is a dimensionless quantity, meaning it has no units. It is a ratio of the force of friction between two bodies and the force pressing them together.

Question 17

A block is placed on a plane whose angle of inclination is 30º.The coefficients of static and kinetic friction for the block on the inclined plane are both 0.2.The block

Accepted Answer

The gravitational component down the plane (mg sin 30º) is greater than the maximum static friction (0.2 mg cos 30º), causing the block to accelerate down the plane.

Question 18

Four identical blocks are moving on a surface for which the coefficient of kinetic friction between each block and the surface is µ_k.The velocity of each block is indicated by the vector on the block.For which block is the force of friction between the surface and the block greatest?

Accepted Answer

Since all the blocks are identical and have the same coefficient of friction with the surface, the force of friction will be the same for all of them. Therefore, the correct choice is E, the force of friction is the same for all blocks.

Question 19

A block of mass m is pulled in the direction shown in the figure across a rough surface at a constant velocity.The magnitude of the frictional force is

Accepted Answer

The answer of A block of mass m is pulled...

Question 20

A 50-kg block rests on a horizontal surface.The coefficient of static friction $\mu$_a = 0.50.The coefficient of kinetic friction $\mu$_k = 0.35.A force of 250 N is applied as shown.

Accepted Answer

The force applied is 250 N. The force of friction opposing the motion is 0.5 x 50 x 9.8 N = 245 N. Therefore, the net force acting on the block is 5 N to the right, which causes the block to accelerate. The acceleration can be calculated using Fnet = ma, where Fnet = 5 N and m = 50 kg. Therefore, a = Fnet/m = 0.1 m/s2.

Quiz 5: Applications of Newtons Laws

A block of mass m is at rest on an inclined plane that makes an angle of 30º with the horizontal,as shown in the figure.Which of the following statements about the force of static friction is true?

A worker pulls horizontally on a rope that is attached to a 10-kg crate resting on a rough floor.The coefficients of static and kinetic friction are 0.5 and 0.3,respectively.The worker pulls with a force of 40 N.The frictional force exerted by the surface is

A tired worker pushes a heavy (100-kg) crate that is resting on a thick pile carpet.The coefficients of static and kinetic friction are 0.6 and 0.4,respectively.The worker pushes with a force of 500 N.The frictional force exerted by the surface is

A block of wood is pulled by a horizontal string across a rough surface at a constant velocity with a force of 20 N.The coefficient of kinetic friction between the surfaces is 0.3.The force of friction is

An object with a mass of 5.5 kg is allowed to slide from rest down an inclined plane.The plane makes an angle of 30º with the horizontal and is 72 m long.The coefficient of friction between the plane and the object is 0.35.The speed of the object at the bottom of the plane is

A mass M = 5.6 kg on a horizontal table is pulled by a horizontal string that passes over a frictionless pulley to a free-hanging mass m = 3.4 kg.The coefficient of friction between M and the table is 0.28.The acceleration of M is

A heavy truck and a light car are traveling at the same speed on the same roadway.If the coefficients of static friction between their tires and the road are the same,which vehicle will be able to stop in the shortest distance? Assume both have the same braking force.

Which of the following statements is NOT true about friction?

An Atomic Force Microscope consists of a cantilever with a very fine tip on one end.The lever is driven by a piezoelectric motor allowing the tip to scan a surface on an atomic scale.As it scans the surface what is the main frictional force between the tip and the surface?

Which fundamental force(s) gives rise to friction?

A 100-kg block is pushed up a 30º incline that is 10 m long.If the coefficient of friction between the block and the incline is 0.1,the constant force parallel to the incline that is required to move the block from rest at the bottom of the incline to the top in 3 s is approximately

The SI units for the coefficient of friction are

A block is placed on a plane whose angle of inclination is 30º.The coefficients of static and kinetic friction for the block on the inclined plane are both 0.2.The block

Four identical blocks are moving on a surface for which the coefficient of kinetic friction between each block and the surface is µ_k.The velocity of each block is indicated by the vector on the block.For which block is the force of friction between the surface and the block greatest?

Quiz 5: Applications of Newtons Laws

A block of mass m is at rest on an inclined plane that makes an angle of 30º with the horizontal,as shown in the figure.Which of the following statements about the force of static friction is true?

A worker pulls horizontally on a rope that is attached to a 10-kg crate resting on a rough floor.The coefficients of static and kinetic friction are 0.5 and 0.3,respectively.The worker pulls with a force of 40 N.The frictional force exerted by the surface is

A tired worker pushes a heavy (100-kg) crate that is resting on a thick pile carpet.The coefficients of static and kinetic friction are 0.6 and 0.4,respectively.The worker pushes with a force of 500 N.The frictional force exerted by the surface is

A block of wood is pulled by a horizontal string across a rough surface at a constant velocity with a force of 20 N.The coefficient of kinetic friction between the surfaces is 0.3.The force of friction is

An object with a mass of 5.5 kg is allowed to slide from rest down an inclined plane.The plane makes an angle of 30º with the horizontal and is 72 m long.The coefficient of friction between the plane and the object is 0.35.The speed of the object at the bottom of the plane is

A mass M = 5.6 kg on a horizontal table is pulled by a horizontal string that passes over a frictionless pulley to a free-hanging mass m = 3.4 kg.The coefficient of friction between M and the table is 0.28.The acceleration of M is

A heavy truck and a light car are traveling at the same speed on the same roadway.If the coefficients of static friction between their tires and the road are the same,which vehicle will be able to stop in the shortest distance? Assume both have the same braking force.

Which of the following statements is NOT true about friction?

An Atomic Force Microscope consists of a cantilever with a very fine tip on one end.The lever is driven by a piezoelectric motor allowing the tip to scan a surface on an atomic scale.As it scans the surface what is the main frictional force between the tip and the surface?

Which fundamental force(s) gives rise to friction?

A mass m is placed on a rough incline at an angle θ\thetaθ to the horizon.A force F is applied up the incline so that the mass slides up the incline.Using the compass rose,the direction of the frictional force is along

A 100-kg block is pushed up a 30º incline that is 10 m long.If the coefficient of friction between the block and the incline is 0.1,the constant force parallel to the incline that is required to move the block from rest at the bottom of the incline to the top in 3 s is approximately

The SI units for the coefficient of friction are

A block is placed on a plane whose angle of inclination is 30º.The coefficients of static and kinetic friction for the block on the inclined plane are both 0.2.The block

Four identical blocks are moving on a surface for which the coefficient of kinetic friction between each block and the surface is µk.The velocity of each block is indicated by the vector on the block.For which block is the force of friction between the surface and the block greatest?

A block of mass m is pulled in the direction shown in the figure across a rough surface at a constant velocity.The magnitude of the frictional force is

A 50-kg block rests on a horizontal surface.The coefficient of static friction μ\muμ a = 0.50.The coefficient of kinetic friction μ\muμ k = 0.35.A force of 250 N is applied as shown.

Four identical blocks are moving on a surface for which the coefficient of kinetic friction between each block and the surface is µ_k.The velocity of each block is indicated by the vector on the block.For which block is the force of friction between the surface and the block greatest?