19. A rocket ship of rest length 100 m is moving at speed 0.8 C past a timing device which records the time interval between the passage of the front and back ends of the ship. This time interval is:
(A)0.20 με
(B) 0.33 με
(C) 0.25 με
(D) 0.52 με(Ε) 0.69 μs.

15. Two long solenoids (radii 20 mm and 30 mm respectively) carry the same amount of current. The smaller solenoid is mounted inside the larger, along a common axis. It is observed that there is zero magnetic field within the inner solenoid. Therefore, the inner solenoid must have X times as many turns per length as the outer solenoid where X is: (A) 4/9 (B) 2/3 (C) 3/2 (D) 1 (E) 9/4.

16. A copper penny slides on a horizontal frictionless table. There is a square region of uniform magnetic field perpendicular to the table as shown. Which graph correctly shows the speed v of the penny as a function of time t? (A) (B) (C) (D) (E)

17. In the circuit shown, switch S is first pushed up to charge the capacitor. When S is then pushed down, the current in the circuit will oscillate at a frequency of:(A) 0.01 Hz (B) 318 Hz (C) 12.6 kHz (D) 2000 Hz (E) depends on Vo.

18. Consider: radio waves (r), visible light (v), infra-red (i), x-rays (x), ultraviolet (u). In order of increasing frequency, they are: (A) r, v, i, x, u (B) i, r, v, u, x (C) r, i, v, u, x (D) i, v, r, u, x (E) r, i, v, x, u.

20. Three different monochromatic light sources are used to liberate free electrons from the surface of an unknown material. Source 1 has wavelength 500 nm, and a stopping potential of 1.08 volts is observed. Source 2 has wavelength 650 nm and a stopping potential of 0.510 volts. If source 3 has wavelength 590 nm, what is the maximum energy of electrons that can be liberated from the surface by source 3? Answer in electron volts. (A) 0.50 (B) 0.70 (C) 0.20 (D) 0.90 (E) 0.10

1. Which of the following statements regarding the reaction force is false?(A) The reaction force of the centripetal force is the centrifugal force.(B) As to the force that the earth attracts the moon, the reaction force is the one that the moon attracts the earth.(C) The Lorentz force violates Newton's third law without considering the contribution of the field.(D) Newton's third law is compatible with conservation of linear momentum.

2. Consider a yoyo of mass m and moment of inertia βmR² rolling without slipping on a surface in the figure. The radius of the large disk is 2R. A string wrapping the axis of radius R is pulled by a force to the right. Setting the direction of F to be positive. The linear acceleration of the center of mass of the yoyo is then given by(A)(B)(C) (D)

3. A rocket of mass M (including fuel) in space is accelerating from rest by ejecting the fuel at a velocity -u relative to the rocket. What is the speed of the rocket when its mass becomes M/2?(A) u/2(B) u ln 2(C) 3u/2(D) u ln

4. A billiard ball hits another ball at rest of identical mass on a surface, making the latter to leave at an angle of 37° relative to the incident direction of the first ball. Suppose the incident speed is u. What is the speed of the first ball after collision?(A) 0.36u(B) 0.6u(C) 0.64u(D) 0.8u.

5. A bomb explodes and breaks into two pieces of mass ratio 2:1. Neglect the mass of the explosive chemicals. What is the ratio of the kinetic energy obtained by the two pieces?(A) 1:2(B) 2:1(C) 4:1(D) 1:3.