Question 1

What force is needed to make an object move in a circle?
A)kinetic friction
B)static friction
C)centripetal force
D)weight
E)tension

Accepted Answer

Centripetal force is the force that keeps an object moving in a circle. It is directed towards the center of the circle and is equal to the mass of the object times the square of its velocity divided by the radius of the circle.

Question 2

When an object moves at constant speed on a circular path, which of the following is true?
A)A net force pointing along the direction of motion acts on the object.
B)A net force pointing along the opposite direction of motion acts on the object.
C)A net force pointing away from the center of the circle acts on the object.
D)A net force pointing towards the center of the circle acts on the object.
E)The net force acting on the object is zero.

Accepted Answer

When an object moves in a circular path at constant speed, it experiences centripetal force, which acts towards the center of the circle.

Question 3

A 55.0-kg box rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.300. What horizontal force must be applied to the box for it to start sliding along the surface?

Accepted Answer

The answer of A 55.0-kg box rests on a horizontal...

Question 4

FIGURE 5-1 
-What type of acceleration does an object moving with constant speed in a circular path experience?
A)free fall.
B)terminal acceleration.
C)constant acceleration.
D)linear acceleration.
E)centripetal acceleration.

Accepted Answer

An object moving with constant speed in a circular path experiences centripetal acceleration, which is the acceleration directed towards the center of the circle. This acceleration is perpendicular to the velocity of the object and is required to keep the object moving in a circular path.

Question 5

FIGURE 5-2 
-Fig. 5-2 indicates the current position of an object traveling at constant speed clockwise around the circle. Which arrow best represent the direction of the current acceleration of the object?
A)

B)

C)

D)

E)

Accepted Answer

The answer of FIGURE 5-2 
-Fig. 5-2 indicates the current...

Question 6

A 60.0-kg mass person wishes to push a 100-kg mass box across a level floor. The coefficient of static friction between the person's shoes and the floor is 0.700. What is the maximum coefficient of static friction between the box and the floor such that the person can push horizontally on the box and cause it to start moving?
A)0.375
B)0.600
C)0.420
D)0.625
E)0.700

Accepted Answer

The answer of A 60.0-kg mass person wishes to push...

Question 7

The banking angle in a turn on the Olympic bobsled track is not constant, but increases upward from the horizontal. Coming around a turn, the bobsled team will intentionally "climb the wall," then go lower coming out of the turn. Why do they do this?
A)to give the team better control, because they are able to see ahead of the turn
B)to prevent the bobsled from turning over
C)to take the turn at a faster speed
D)to take the turn at a slower speed
E)to reduce the g-force on them

Accepted Answer

Increasing the banking angle allows the bobsled team to take the turn at a faster speed without sliding off the track. Climbing the wall at the start of the turn also helps to keep the bobsled from turning over, as it allows the team to maintain their momentum through the turn while staying on the track. Lowering the banking angle coming out of the turn helps to reduce the G-forces on the team.

Question 8

FIGURE 5-1 
-For an object that travels at a fixed speed along a circular path, the acceleration of the object is
A)larger in magnitude the smaller the radius of the circle.
B)in the same direction as the velocity of the object.
C)smaller in magnitude the smaller the radius of the circle.
D)in the opposite direction of the velocity of the object.
E)zero.

Accepted Answer

The answer of FIGURE 5-1 
-For an object that travels...

Question 9

FIGURE 5-3 
-Two masses are connected by a string which goes over an ideal pulley as shown in Fig. 5-3. Block A has a mass of 3.00 kg and can slide along a rough plane inclined 30.0° to the horizontal. The coefficient of static friction between block A and the plane is 0.400. What mass should block B have in order to start block A sliding up the ramp?

Accepted Answer

The answer of FIGURE 5-3 
-Two masses are connected by...

Question 10

When an object experiences uniform circular motion, the direction of the net force is
A)in the same direction as the motion of the object.
B)in the opposite direction of the motion of the object.
C)is directed toward the center of the circular path.
D)is directed away from the center of the circular path.
E)is dependent on the speed of the object.

Accepted Answer

According to the concept of centripetal force, the net force acting on an object undergoing uniform circular motion is directed towards the center of the circular path. This force is necessary to continuously change the direction of the object's velocity to keep it moving in a circular path. Therefore, the correct choice is C.

Question 11

Is it possible for an object moving around a circular path to have both centripetal and tangential acceleration?
A)No, because then the path would not be a circle.
B)No, an object can only have one or the other at any given time.
C)Yes, this is possible if the speed is constant.
D)Yes, this is possible if the speed is changing.

Accepted Answer

Centripetal acceleration is due to the change in direction of velocity, while tangential acceleration is due to the change in the magnitude of velocity. If the speed is changing, both accelerations can exist simultaneously.

Question 12

When an object experiences uniform circular motion, the direction of the acceleration is
A)in the same direction as the velocity vector.
B)in the opposite direction of the velocity vector.
C)is directed toward the center of the circular path.
D)is directed away from the center of the circular path.
E)depends on the speed of the object.

Accepted Answer

According to the equation for centripetal acceleration, a = v^2 / r, the acceleration is directed toward the center of the circular path. This is because the velocity vector is always tangent to the circular path, and the acceleration vector is perpendicular to the velocity vector and directed inward toward the center of the circle.

Question 13

When a parachutist jumps from an airplane, he eventually reaches a constant speed, called the terminal velocity. This means that
A)the acceleration is equal to g.
B)the force of air resistance is equal to zero.
C)the effect of gravity has died down.
D)the effect of gravity increases as he becomes closer to the ground.
E)the force of air resistance is equal to the weight of the parachutist.

Accepted Answer

At terminal velocity, the force of air resistance (also called drag) acting on the parachutist is equal to the weight of the parachutist. This means that the net force acting on the parachutist is zero, causing him to no longer accelerate and instead maintain a constant speed. This does not mean that the effect of gravity has died down or that the acceleration is equal to g, as gravity is still acting on the parachutist and causing him to move downwards at a constant speed.

Question 14

A car of mass m goes around a banked curve of radius r with speed v. If the road is frictionless due to ice, the car can still negotiate the curve if the horizontal component of the normal force on the car from the road is equal in magnitude to A)mg/2. B)mg. C)mg sinθ . D)mv²/r. E)tan[v²/(rg)].

Accepted Answer

The horizontal component of the normal force provides the necessary centripetal force for the car to negotiate the curve. This force is equal to mv²/r, which is the centripetal force required for circular motion.

Question 15

Consider a particle moving with constant speed such that its acceleration of constant magnitude is always perpendicular to its velocity.
A)It is moving in a straight line.
B)It is moving in a circle.
C)It is moving in a parabola.
D)It is moving in a hyperbola.
E)None of the above is definitely true all of the time.

Accepted Answer

Since the acceleration is always perpendicular to the velocity, the motion is always perpendicular to the acceleration. This means that the motion is always circular, because the only path that maintains a constant distance from a fixed point is a circle.

Question 16

FIGURE 5-2 
-Fig. 5-2 indicates the current position of an object traveling at constant speed clockwise around the circle. Which arrow best represent the direction the object would travel if the centripetal force was suddenly reduced to zero?
A)

B)

C)

D)

E)

Accepted Answer

The answer of FIGURE 5-2 
-Fig. 5-2 indicates the current...

Question 17

As a car drives with its tires rolling freely without any slippage, the type of friction acting between the tires and the road is
A)static friction.
B)kinetic friction.
C)a combination of static and kinetic friction.
D)neither static nor kinetic friction, but some other type of friction.
E)It is impossible to tell what type of friction acts in this situation.

Accepted Answer

When a car drives with its tires rolling freely without any slippage, the type of friction acting between the tires and the road is static friction. This is because the tires are not slipping or moving relative to the road, so the friction between them is static.

Question 18

For very small objects at very low speeds, the drag force is directly proportional to the magnitude of the velocity. The proportionality constant depends on
A)the viscosity of the fluid.
B)the size of the object.
C)the shape of the object.
D)all of the above choices.
E)none of the above choices.

Accepted Answer

The drag force for small objects at low speeds is described by Stokes' Law, which states that the drag force is proportional to the viscosity of the fluid, the size of the object, and the shape of the object.

Question 19

A 55-kg box rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.30. A 140-N force is applied to the box. What is the frictional force on the box?

Accepted Answer

The answer of A 55-kg box rests on a horizontal...

Question 20

A car goes around a curve at a constant speed. What is the direction of the net force on the car?
A)toward the curve's center
B)away from the curve's center
C)toward the front of the car
D)toward the back of the car
E)the net force is zero

Accepted Answer

When a car goes around a curve at a constant speed, it is undergoing centripetal acceleration, which means the net force is directed toward the center of the curve.

Quiz 5: Using Newtons Laws: Friction, Circular Motion, Drag Forces

What force is needed to make an object move in a circle?

When an object moves at constant speed on a circular path, which of the following is true?

A 55.0-kg box rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.300. What horizontal force must be applied to the box for it to start sliding along the surface?

FIGURE 5-1 -What type of acceleration does an object moving with constant speed in a circular path experience?

FIGURE 5-2 -Fig. 5-2 indicates the current position of an object traveling at constant speed clockwise around the circle. Which arrow best represent the direction of the current acceleration of the object?

The banking angle in a turn on the Olympic bobsled track is not constant, but increases upward from the horizontal. Coming around a turn, the bobsled team will intentionally "climb the wall," then go lower coming out of the turn. Why do they do this?

FIGURE 5-1 -For an object that travels at a fixed speed along a circular path, the acceleration of the object is

When an object experiences uniform circular motion, the direction of the net force is

Is it possible for an object moving around a circular path to have both centripetal and tangential acceleration?

When an object experiences uniform circular motion, the direction of the acceleration is

When a parachutist jumps from an airplane, he eventually reaches a constant speed, called the terminal velocity. This means that

A car of mass m goes around a banked curve of radius r with speed v. If the road is frictionless due to ice, the car can still negotiate the curve if the horizontal component of the normal force on the car from the road is equal in magnitude to

Consider a particle moving with constant speed such that its acceleration of constant magnitude is always perpendicular to its velocity.

FIGURE 5-2 -Fig. 5-2 indicates the current position of an object traveling at constant speed clockwise around the circle. Which arrow best represent the direction the object would travel if the centripetal force was suddenly reduced to zero?

As a car drives with its tires rolling freely without any slippage, the type of friction acting between the tires and the road is

For very small objects at very low speeds, the drag force is directly proportional to the magnitude of the velocity. The proportionality constant depends on

A 55-kg box rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.30. A 140-N force is applied to the box. What is the frictional force on the box?

A car goes around a curve at a constant speed. What is the direction of the net force on the car?