AP Physics C: Mechanics - Unit 2 Progress Check MCQ

A roller coaster has a circular loop of radius r. The minimum speed of a coaster car at the top of the loop needed to make it through the loop without losing contact is vmin⁡. Which of the following is an expression for the radius of the loop that has a minimum speed of 2vmin?

A. 4r

The figure represents an amusement park ride that consists of three spokes of radius R1=12m spinning at a constant rate. At the end of each of the three spokes are four smaller spokes holding a passenger seat at a radius R2=4.0m, also spinning at a constant rate. At the instant shown, a 35 kg child is in cart A, moving with a speed of 7.5ms. Which of the following is most nearly the magnitude of the force on the child?

A. 120 N

A particle is moving with a constant velocity in the +x-direction. When the particle reaches the origin, a constant force is exerted on it in the +y-direction. Which of the following graphs best shows the path the particle will follow?

A. Parabolic Up. Since the force is in the y-direction, the particle will continue to move at a constant speed in the x-direction and accelerate in the y-direction. This will create a parabolic path around the y-axis.

Two blocks are connected by a light string, as shown in Figure 1. There is friction between the blocks and the table. The system is released from rest, and the blocks accelerate. The tension in the string is T1. Then the setup is returned to its starting position, and a third block is attached as shown in Figure 2. The masses of the blocks are related as follows: M1>M2>M3. The system is again released from rest and allowed to accelerate. The tension in the string on the left is T2. Which of the following gives a correct relationship between the tensions in the string on the left in the two situations?

A. T1 < T2

A coin of mass mm is placed a distance r from the center of a horizontal turntable, as shown in the figure. Turntable 1, which has negligible friction, is turned on and spins at a rate such that the point where the coin is placed moves with speed v. When the coin is placed at this point, it slides off turntable 1. The coin is then placed a distance r from the center of turntable 2 that has a rough surface with a coefficient of friction μsμs. Which of the following describes the change in the motion of the coin as it moves on turntable 2 as compared to turntable1?

A. The coin is accelerated toward the center of turntable 2 if μs≥v^2/gr.

Blocks 1, 2, and 3 on a horizontal surface of negligible friction are being pushed by a force of magnitude F. The blocks have the masses indicated in the figure with M1>M2>M3. The accelerations of blocks 1, 2, and 3 are a1, a2, and a3, respectively. F12 is the force block 1 exerts on block 2 is F23 is the force block 2 exerts on block 3. Which of the following indicates data that support the claim that F12>F23?

A. a1 = a2 = a3; since M2+M3>M3, then F12>F23.

A block is sliding on a curved surface ramp with non-negligible friction, as shown in the figure. The acceleration vector a→ of the block as it is moving to the right past point P is shown. Which of the following best describes the motion of the block at point P?

B. The block is slowing down and changing direction.

A person is standing on a scale placed on the floor of an elevator. At time t1t1, the elevator is at rest and the reading on the scale is 500N. At a later time t2, the person is still standing on the scale and the reading on the scale is 400N . Based on the scale readings, which of the following statements about the motion of the elevator could be true at time t2?

B. The elevator is moving upward and slowing down.

A ball is thrown straight down from the top of a building with a speed greater than its terminal speed vT. Which of the following graphs best represents the speed v of the ball as a function of time t while it falls to the ground?

C. Above, decreasing towards and almost touching Vt. The ball starts with a speed greater than the terminal velocity, and the speed should decrease to a value approaching the terminal speed.

The figure shows blocks C and D on a horizontal surface in contact with each other. A force F is applied to block C. In which of the following situations does block D apply a force of magnitude 1/3F to block C?

C. Block C: 2m Block D: m

A block of mass m is being pushed up a rough inclined plane by a force of magnitude F. The magnitude of the friction force between the block and the surface is μ. The plane makes an angle θ with the horizontal. Which of the following equations can be used to solve for the acceleration of the block?

C. F - f - mgsinθ = ma

A block of mass mm is initially at rest on a rough horizontal surface when a constant force F is exerted on it, as shown. The block accelerates to the right and is moving with speed v once it has moved a distance d. Which of the following equations can be used to solve for the force of friction exerted on the block by the surface?

C. F - f = mv^2/2d

Blocks A and B of masses m and 2m, respectively, are connected by a light string and are pulled along a horizontal surface of negligible friction by a horizontal force of magnitude F, as shown in the figure. The tension in the string is T. If the masses of the blocks are doubled, and the magnitude of the horizontal force remains the same, the tension in the string will be

C. T

A block of mass m is initially moving on a rough horizontal surface as shown in Figure 1. Figure 2 shows the four forces acting on the block. Which of the following best describes the motion of the block at the moment shown in the two figures?

C. The block is moving to the right and slowing down.

A wood block is placed on a rough surface. The surface starts horizontal, and one end is then raised so that the angle the surface makes with the horizontal gradually increases until, at an angle θ, the block begins to move down the surface, as shown in the figure. From this observation, which of the following can be concluded for angles greater than θ ?

C. The component of the gravitational force along the surface is greater than the frictional force.

The diagram above shows an overhead view of a 450kg car traveling clockwise at a constant speed along a flat horizontal circular track of radius 50m . The car takes 25s to complete one lap around the track. Which of the following gives the magnitude and direction of the force of friction exerted on the car by the track at the moment shown in the figure?

D. 1420 N to the left

A person is cleaning a wall by pushing a brush against the wall, as shown in the figure. The person is pushing the brush upward with an increasing speed. Which of the following free-body diagrams best represents the motion described?

D. 3 vectors. This figure shows a vector pointing up and to the right. The component to the right is approximately equal to the vector to the left. The component upward is greater than the vector downward. This would indicate a net force and acceleration directed upward. Thus, if the brush is moving upward, it will be speeding up.

Blocks A and B of masses M and 3M, respectively, are on a horizontal surface of negligible friction. A horizontal force FA is exerted on block A, as shown. If the force exerted by block B on block A has a magnitude F, the magnitude of FA is

D. 4/3 F

Block A of mass M is on a horizontal surface of negligible friction. An identical block B is attached to block A by a light string that passes over an ideal pulley. The tension force exerted on block A after the system is released from rest has magnitude T. Block B is then replaced by a block of mass 2M and the system again released from rest.. Which of the following is a correct expression for the tension force now exerted on block A?

D. 4/3 T

Box A has a weight of 5N and is at rest on a horizontal floor. Box B has a weight of 2N and is at rest on top of box A. Which of the following free-body diagrams is correct for the two boxes?

E. F floor-on-A = 7 N F B-on-A = 2 N F weight-A = 5 N F A-on-B = 2 N F weight-B = 2 N

In experiment 1, a cart of mass m, initially at rest, is pulled by a force of magnitude F0 , as shown in Figure 1, for a time t0 to give the cart a speed v. In experiment 2, a cart of mass m, initially at rest, is pulled by a force F, as shown in Figure 2, for a time 2t0 to give the cart speed v. Which of the following gives a correct equation for the magnitude of F and explains the equation based on experimental evidence?

E. F=1/2F0. Because it took the cart twice the time to reach the same speed, it has half the acceleration and therefore half the force.

Blocks A and B of unknown masses m1 and m2, respectively, are set up on an inclined plane as shown. Block A is attached to block B by a light string that passes over an ideal pulley. Block A is on a surface of negligible friction. The blocks are released from rest, block A accelerates up the incline, and its acceleration aa is measured. Which of the following uses the data for the magnitude of the acceleration to support a correct claim about the masses of the blocks?

E. It cannot be determined which block has more mass from the information provided.

The drag force on a falling coffee filter can be modeled as a linear function with respect to velocity, FD→=−bv, where b is a positive constant related to the surface area and shape of the coffee filter. The teacher demonstrates how the value of constant bb can be determined by releasing coffee filters from rest and having them fall toward a motion detector, as shown. The students repeat the activity and use the motion detector to measure the position, velocity, and acceleration of different coffee filters as they fall. Which of the following would provide the data needed to determine the value of b?

E. Stack multiple coffee filters in order to vary the weight of the system without changing the surface area and measure the terminal velocity of the coffee filters.

An Atwood's machine is set up as shown in the figure. The blocks have the masses indicated, and the pulley has negligible mass and friction. Which of the following claims best describes the motion of the block of mass 3m and provides appropriate reasoning?

E. The block will accelerate upward with magnitude a<g, because the force of gravity on it will be less than the tension in the string.

Blocks A and B are connected by a light string and are pulled up an inclined plane at constant speed by a force of magnitude F. The inclined plane makes an angle θ with the horizontal, as shown. The angle is slowly increased, and the magnitude of the force F is adjusted so that the blocks continue to move up the incline at constant speed. Which of the following makes a correct claim about the tension in the string between the blocks and provides evidence to support that claim?

E. The tension in the string will increase because the component of the gravitational force parallel to the plane increases.

A person stands against the wall inside an amusement park ride consisting of a large cylinder that can spin about its central axis. When the cylinder is spinning at a high enough constant speed, the floor drops, but the person remains at the same location on the wall without slipping. From the perspective shown in the top view, which of the following illustrates the correct direction of the velocity v and acceleration a of the person at the position indicated when the cylinder is spinning in the direction shown?

E. Velocity pointing downwards, acceleration pointing right