AP Physics Unit 2 Progress Check: MCQ Part B

Block A of mass 4m is attached by a light string to block B of mass 2m. The string passes over a pulley with negligible friction and of negligible mass. Block A is held a distance h above the ground, as shown. The blocks are released from rest, and block A reaches the ground two seconds later. The value of h is most nearly

6.7m

A 3kg object experiences a rightward horizontal acceleration of 6m/s2 as it slides to the right across a rough, horizontal surface. The table above contains the label and magnitude of four forces exerted to the right or left on the object that represent measurements from an experiment as the object accelerates. Which pair of opposing forces in which directions could be responsible for the acceleration of the object?

F3 to the right and F2 to the left

A falling skydiver opens his parachute. A short time later, the weight of the skydiver-parachute system and the drag force exerted on the system are equal in magnitude. Which of the following statements predicts the motion of the skydiver at this time?

The skydiver is moving downward with a constant speed

An object of mass M is dropped near the surface of Earth such that the gravitational field provides a constant downward force on the object. Which of the following describes what happens to the center of mass of the object-Earth system as the object falls downward toward Earth?

it does not move

The following figures each show vectors representing the forces exerted on an object that is initially at rest. In which case will the object remain at rest?

one with the diagonal arrow sticking out of the upper left

A block slides with constant velocity down a rough inclined plane that makes an angle of θ with the horizontal. It experiences three forces: gravitational (Fg), normal (FN), and frictional (Ff). Which of the following gives the magnitude of the net force on the block?

zero

Three boxes are pulled to the left by strings with negligible mass on a horizontal surface, as shown above. The masses of the boxes are m1, m2, and m3, where m3>m2>m1. Friction between the boxes and the surface is negligible. The figure below shows force diagrams for each box. Given that m3>m2>m1, how do the force F and string tensions TA and TB compare?

Tb<ta<F

Two astronauts of identical mass are connected by a taut cable of negligible mass, as shown in the figure above, and are initially at rest with respect to a nearby space station. Astronaut Y pulls on the cable toward herself with considerable force. Which of the following describes the direction of the velocity of the center of mass of the two astronauts after Astronaut Y pulls on the cable?

the center of mass does not move

A hockey player uses a hockey stick to hit a puck such that the stick provides an applied force on the puck. The puck travels for distance of 0.85m while experiencing the force from the stick. The puck leaves the stick with a speed of 8.0m/s and travels at constant speed in a straight line along the horizontal ice for a distance of 12m. The frictional force between the puck and the ice surface is negligible. Which of the following statements best describes the force or forces exerted on the puck after it is hit by the stick and slides on the ice?

There is no frictional force exerted on the puck, and the gravitational force and normal force are exerted on the puck and are equal in magnitude.

In the setup shown in the figure, two blocks of equal mass M are at rest but are just about to slip. Also shown is a free-body diagram for the block on top of the table. In this setup, the coefficient of static friction between the table and the block resting upon it must be

at least 1.0

Two blocks of mass 2 kg and 3 kg are connected by a light string that passes over a pulley, as shown above. The pulley has negligible mass and friction. The two-block system is released from rest. Which of the following correctly describes the velocity of the two-block system's center of mass?

downward, increasing

A 1kg block is placed near the top of an inclined plane that is at an angle of 30 degrees with respect to the ground, as shown above. By correctly determining the effect of gravity, a student predicts that the acceleration of the block will be 5m/s2. After allowing the block to slide down the inclined plane, the student finds that the acceleration is actually 4m/s2. What type of force did the student most likely not account for when predicting the acceleration of the block, and what is the magnitude of that force?

force of friction of approx. 1 N

Three boxes are pulled to the left by strings with negligible mass on a horizontal surface, as shown above. The masses of the boxes are m1, m2, and m3, where m3>m2>m1. Friction between the boxes and the surface is negligible. The figure below shows force diagrams for each box. A student is trying to determine the tensions in the strings connecting the boxes. If the acceleration of the system and the pulling force F are known, which of the following pairs of equations could be used to find the tensions?

m3a3 = Tb & m2a2 = Ta - Tb

A person kicks a ball into the air with a force F0. The figure shows the position of the ball at various times. What is the net force on the ball and its acceleration at the highest point shown?

mg, g

Three blocks are sliding together to the right along a surface of negligible friction when a force with magnitude Fext is exerted to the left on the rightmost block, as shown in the figure. The masses of the blocks are indicated in the figure. If the force is exerted for a time Δt, what is the change in velocity of the center of mass of the three-block system?

Fext/6m delta t

Three boxes are pulled to the left by strings with negligible mass on a horizontal surface, as shown above. The masses of the boxes are m1, m2, and m3, where m3>m2>m1. Friction between the boxes and the surface is negligible. The figure below shows force diagrams for each box. Which of the following is a correct ranking of the normal forces Fn1, Fn2, and Fn3 exerted on the boxes?

Fn3>Fn2>Fn1

A motorized cart is attached to a string that passes over a pulley. The other end of the string is attached to a hanging block. In the figure shown above, the cart is accelerating to the right. Which of the following best represents the forces acting on the cart at the instant shown?

Fnormal, Ftension, and Fgravity all have same length arrow, Fapplied is longer

A hockey player uses a hockey stick to hit a puck such that the stick provides an applied force on the puck. The puck travels for distance of 0.85m while experiencing the force from the stick. The puck leaves the stick with a speed of 8.0m/s and travels at constant speed in a straight line along the horizontal ice for a distance of 12m. The frictional force between the puck and the ice surface is negligible. How does the magnitude of the force exerted by the stick on the puck Fpuck,stick compare to the magnitude of the force exerted by the puck on the stick Fstick,puck at the time interval in which the stick is in contact with the puck?

Fpuck,stick = Fstick,puck

Three blocks with masses m1, m2, and m3 are attached by strings, as shown in the figure above. The coefficient of friction between each of the blocks and the horizontal surface is μ. The tension in the left and right strings is T2 and T1, respectively. If the acceleration of the blocks is a, which of the following expressions is equal to T2 ?

T1-m2a-mum2g

Three boxes are pulled to the left by strings with negligible mass on a horizontal surface, as shown above. The masses of the boxes are m1, m2, and m3, where m3>m2>m1. Friction between the boxes and the surface is negligible. The figure below shows force diagrams for each box. Students attach a force probe in the middle of string A to measure TA and then use a different force probe to provide the applied force F to the box of mass m1. With the box of mass m3 held in place by one student, a second student pulls to the left on the force probe that provides the applied force F. As the second student pulls with a steady force, and with the boxes remaining at rest, the following pairs of readings from the two force probes are recorded at different times. Based on the measurements above, how do the magnitudes of the two force quantities compare?

The two quantities agree within experimental uncertainty but do not exactly agree numerically

Two ice skaters, Skater X and Skater Y, are at rest on a horizontal surface made of ice. The friction between the ice and the skaters is negligible. Skater X, who has a smaller mass than Skater Y, pushes Skater Ysuch that Skater Y travels with a speed of 2vo to the right. Which of the following indicates the direction of the velocity of Skater X and the direction of the velocity of the center of mass of the two-skater system after the push?

to the left, zero