¿AP Physics? ¡Si!

A person of mass M is running at a speed of and jumps onto a stationary sled of equal mass M on a frozen lake as shown. What percent of the system’s kinetic energy is lost as a result of jumping on the sled?

• 0%

• 50%

• 25%

• 75%

Waluigi launches a golf-ball at cliff twice. In both cases the ball is hit the exact same way. The first time the ball is hit, the ball hits the cliff at point A, which is a height of h above the ground. The second time the ball is hit (with the same launch angle and launch speed), the ball explodes into two pieces of equal mass in the air right after being hit. One piece lands at point B, a height of 2h above the ground. At what height, y, does the other piece hit the cliff?

• Between the ground and point A, 0 < y < h

• At point A, y=h.

• Between points A and B, h < y < 2h

• At ground level, y = 0

A Waluigi logo consisting of two equal 2D rectangular masses is placed on a coordinate system as shown. What is the location of the center of mass of the Waluigi logo?

• (1.0, 2.5)

• (1.25, 2.5)

• (1.5, 2.5)

• (1.0, 2.75)

A go-kart of mass M collides with an identical go-kart of mass M as shown. The trailing go-kart is going at 3 m/s before the collision and the leading go-kart is going at 2 m/s in the same direction. After the two go-karts collide and separate, the leading go-kart now is going at 3 m/s and the trailing go-kart goes at 2 m/s in the same direction. Which of the following is true of the collision?

• It is elastic because momentum is conserved.

• It is elastic because kinetic energy is conserved.

• It is inelastic because momentum is not conserved.

• It is inelastic because kinetic energy is not conserved.

Two carts of equal mass are on a horizontal surface with negligible friction. Cart A is approaching cart B, which is at rest, as shown in Figure 1 above. Attached to cart B is a spring that is initially compressed. At the moment cart A collides with cart B, the spring is released and pushes on cart A, as shown in Figure 2 above. Which of the following correctly states what happens to the kinetic energy and the momentum of the two-cart system as a result of the collision compared to those quantities before the collision?

• KE - Increases Momentum - Increase

• KE - Increases Momentum - Stays the same

• KE - Decreases Momentum - Increase

• KE - Stays the same Momentum -Stays the same

An object of mass m moves with speed v towards stationary mass M. What is the speed of the center of mass of the system?

• $\left(\frac{m}{m+M}\right)v$

• $\left(1+\frac{m}{M}\right)v$

• $\left(1+\frac{M}{m}\right)v$

• $\left(\frac{M}{M+m}\right)v$

Two blocks are sliding toward one another along a level horizontal surface. One block is moving due east, and the other block is moving due west. The two blocks collide. Which of the following is NOT a possible set of directions the two blocks could be traveling after the collision?

• Both blocks are traveling east after the collision.

• One block travels northeast, and the other block travels northwest.

• One block travels southwest, and the other block travels northeast.

• One block travels southeast, and the other block travels northwest.

A dart of mass 0.2 kg is launched from ground level at speed 10 m/s at an angle of 30 degrees above the horizontal as shown. At the apex of the dart’s trajectory, it strikes and sticks to a block of mass 2.0 kg, which is attached to a 1.2 m string. What maximum angle does the string make with the vertical after being the block is struck by the dart?

• 62 degrees

• 22 degrees

• 38 degrees

• 13 degrees

At one moment in time, a cart full of water has a total mass of 30 kg. Due to a water leak, water leaks out of the cart at a rate of 0.5 kg/s. The cart moves to right at 8 m/s. Due to the water leak, it’s velocity is increasing at a rate of 1.0 m/s. Calculate the total force on the cart at this instant.

• 34 N

• 26 N

• 30 N

• 22 N

Waluigi drops a 0.2 kg bouncy ball from a height 20 m. It rebounds and reaches a maximum height of 5 m. What is the magnitude of the impulse that the ground exerts on the ball?

• 6.0 Ns

• 4.0 Ns

• 3.0 Ns

• 2.0 Ns