Translational Kinetic Energy AP Physics 1 FRQ – Exam Style Questions etc.
Translational Kinetic Energy AP Physics 1 FRQ
Unit: 3. Work , Energy and Power
Weightage : 10-15%
Exam Style Practice Questions, Translational Kinetic Energy AP Physics 1 FRQ
Question
The figure presents a block with a mass of M located at the top of a curved ramp. The top of the ramp has a height of h to the horizontal, and the ramp has a length of L. Students set up an experiment with a small block on an ramp. The block of mass M=3.0 kg is released from rest at the top of the curved ramp. The length of the ramp as measured along the curve is L=3.0 m, and the height is h=1.5 m, as shown. There is negligible friction between the small block and the ramp.
The students now move the block to a ramp that is identical to the first one except that it has a rough surface. Figure 1 shows the block as it is sliding
down the ramp. Figure 2 shows a free-body diagram for the block when it is at the moment shown in Figure 1. Which of the following claims is supported by the figures?
A Earth’s gravitational force does less work on the block when it is on the first ramp with the rough surface.
B Earth’s gravitational force does more work on the block when it is on the first ramp with the rough surface.
C Friction does negative work on the block.
D Friction does positive work on the block.
E The normal force does positive work on the block.
Answer/Explanation
Ans:C
The frictional force is against the motion of the block; thus, it will do negative work on the block as the block travels down the incline.
Question
Cart A is traveling east when it collides with cart B, which is traveling north. Cart A has a mass of 3.05kg, and cart B has a mass of 2.10kg. The two carts travel together as a single object on a horizontal surface at an angle θ relative to due east, as shown above.
In another trial, the speed of the carts immediately after the collision is 0.60 m/s, and the carts slide 0.24m on the horizontal surface before coming to rest. The coefficient of kinetic friction between the sliding carts and the surface is most nearly
A \(0.08\)
B \(0.13\)
C \(0.19\)
D \(0.25\)
E \(0.75\)
Answer/Explanation
Ans:A
Setting the energy dissipated equal to the change in kinetic energy yields
\(E=fd\)
\(=ΔK=\frac{1}{2}m(v_f^2−v_i^2)=\frac{1}{2}m(0−v_i^2)\)
\(−μmgd=−\frac{1}{2}mv_i^2\)
\(μ=\frac{v_i^2}{2gd}=\frac{(0.6m/s)^2}{2(9.81m/s^2)(0.24m)}=0.08\)
Question
Suppose that a hole is drilled through the center of Earth to the other side along its axis. A small object of mass m is dropped from rest into the hole at the surface of Earth, as shown above. If Earth is assumed to be a solid sphere of mass M and radius R and friction is assumed to be negligible, correct expressions for the kinetic energy of the mass as it passes Earth’s center include which of the following ?
I. \(\frac{1}{2}MgR\)
II. \(\frac{1}{2}mg\)
III. \(\frac{GmM}{2R}\)
A I only
B II only
C III only
D I and III only
E II and III only
Answer/Explanation
Ans:E
Question
A descending elevator of mass 1,000 kg is uniformly decelerated to rest over a distance of 8 m by a cable in which the tension is 11,000 N. The speed vi of the elevator at the beginning of the 8 m descent is most nearly
A \(4 m/s\)
B \(10 m/s\)
C \(13 m/s\)
D \(16 m/s\)
E \(21 m/s\)
Answer/Explanation
Ans:A
Question
Two pucks moving on a frictionless air table are about to collide, as shown above. The 1.5 kg puck is moving directly east at 2.0 m/s. The 4.0 kg puck is moving directly north at 1.0 m/s.
What is the total kinetic energy of the two-puck system before the collision?
A \(\sqrt{13} J\)
B \(5.0 J\)
C \(7.0 J\)
D \(10 J\)
E \(11 J\)
Answer/Explanation
Ans:B