wu-ap-physics1

化学 (UKChO)
宏观经济
微观经济
统计AB
统计BC
物理3电磁学
物理3力学
物理2
物理1
生物
化学

An object is moving in the positive x-direction while a net force directed along the x-axis is exerted on the object. The figure above shows the force as a function of position.

What is the net work done on the object over the distance shown？

F₀d

3 F₀d/2

2 F₀d

4 F₀d

The diagram above shows a top view of a child of mass M on a circular platform of mass 2M that is rotating counter clockwise. Assume the platform rotates without

friction. Which of the following describes an action by the child that will increase the angular speed of the platform-child system and gives the correct reason why？

The child moves toward the center of the platform, increasing the total angular momentum of the system.

The child moves toward the center of the platform, decreasing the rotational inertia of the system.

The child moves away from the center of the platform, increasing the total angular momentum of the system.

The child moves away from the center of the platform, decreasing the rotational
Inertia of the system.

3. The figure above shows the forces exerted on a block that is sliding on a horizontal surface: the gravitational force of 40N，the 40N normal force exerted by the surface, and a frictional force exerted to the left. The coefficient of friction between the block and the surface is 0.20. The acceleration of the block is most nearly

1.0m/s² to the right

1.0m/s² to the left

2.0m/s² to the right

2.0m/s² to the left

A student on another planet has two identical spheres, each of mass 0.6kg, attached to the ends of a rod of negligible mass. The student gives the assembly a rotation in the vertical plane and then releases it so it falls，as shown in the top figure above. Sensors record the vertical velocity of the two spheres, and the data is shown in the graph of velocity v as a function of time t. Another student wants to calculate the assembly’s angular speed and the change in the linear momentum of the center of mass of the assembly between 0 s and 0.3s. Which of the sequantities can be determined using the graph？

Angular speed only

Change in linear momentum only

Angular speed and change in linear momentum

Neither of these quantities can be determined using the graph.

A block of known mass hanging from an ideal spring of known spring constant is oscillating vertically. A motion detector records the position, velocity, and acceleration of the block as a function of time. Which of the following indicates the measured quantities that are sufficient to determine whether the net force exerted on the block equals the vector sum of the individual forces？

Acceleration only

Acceleration and position only

Acceleration and velocity only

Acceleration，position，and velocity

Block A hangs from a light string that passes over a light pulley and is attached to Block B，which is on a level horizontal frictionless table, as shown above. Students are to determine the mass of block B from the motion of the two-block system after it is released from rest. They plan to measure the time block A takes to reach the floor. The students must also take which of the following measurements to determine the mass of block B？

Only the mass of block A

Only the distance block A falls to reach the floor

Only the mass of block A and the distance block A falls to reach the floor

The mass of block A, the distance block A falls to reach the floor, and the radius of the pulley

Two objects are released from rest at the top of ramps with the same dimensions, as shown in the figure above. The sphere rolls down one ramp without slipping. The small block slides down the other ramp without friction. Which object reaches the bottom of its ramp first, and why？

The sphere, because it gains rotational kinetic energy, but the block does not

The sphere, because it gains mechanical energy due to the torque exerted on it, but the block does not

The block, because it does not lose mechanical energy due to friction, but the sphere

The block，because it does not gain rotational kinetic energy, but the sphere does

8. Two blocks, of mass m and 2m，are initially at rest on a horizontal frictionless surface. A force F is exerted individually on each block, as shown above. The graph shows how F varies with time t. Which block has the greatest average power provided to it between t=0 s and t=3s？

The block of mass m

The block of mass 2m

Both blocks have the same power provided to them.

lt cannot be determined without knowing the ratio of the maximum force to the mass m.

A moon is in an elliptical orbit about a planet as shown above. At point A the moon has speed u_A and is at distance R_A from the planet. At point B the moon has speed u_B .Which of the following explains a correct method for determining the distance of the moon from the planet at point B in terms of the given quantities？

Conservation of angular momentum, because the gravitational force exerted by the moon on the planet is the same as that exerted by the planet on the moon

(B) Conservation of angular momentum, because the gravitational force exerted on the moon is always directed toward the planet

(D) Conservation of energy because the gravitational force exerted by the moon on the planet is the same as that exerted by the planet on the moon

10.

Block 1 of mass and block2 of mass m₂ are sliding along the same line on a horizontal frictionless surface when they collide at time t_c. The graph above shows the velocities of the blocks as a function of time.

Which block has the greater mass, and what information indicates this？

Block 1, because it had a greater speed before the collision.

Block 1, because the velocity after the collision is in the same direction as its velocity before the collision.

Block 2, because it had a smaller speed before the collision.

Block 2, because the final velocity is closer to the initial velocity of block 2 than it is to the initial velocity of block 1.

11. How does the kinetic energy of the two-block system after the collision compare with its kinetic energy before the collision，and why？

It is less, because the blocks have the same velocity after the collision, so some of their kinetic energy was transformed into internal energy.

It is less，because the blocks have velocities in opposite directions before the collision，so some of kinetic energy cancels.

It is the same, because the collision was instantaneous，so the effect of external forces during the collision is negligible.

It is the same, because the blocks have the same velocity after the collision，and there is no friction acting on them.

12. Which of the following is true of the motion of the center of mass of the two-block system during the time shown？

The center of mass does not move because the blocks are moving in opposite directions before the collision.

The center of mass moves at a constant velocity of +1.0m/s because there is no friction acting on the system.

The center-of-mass velocity starts out greater than +1.0m/s but decreases to +1.0m/s during the collision because the collision is inelastic.

The center-of-mass velocity increases as the blocks get closer together, and then becomes constant after the collision.

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