20. When a photon undergoes Compton scattering with an electron and is scattered at a 90° angle relative to its original direction, its energy after scattering is half of its original energy. What is the initial wavelength of the photon?
(A) 1.33 nm
(B) 2.43 nm
(C) 1.33 pm
(D) 2.43 pm
(E) None of the above

16. What is the energy density ratio of electric and magnetic fields in an electromagnetic wave? (A) Equal (B) Electric is twice magnetic (C) Magnetic is twice electric (D) Cannot be compared (E) Depends on frequency

17. A radio station requires a coaxial cable to connect the transmitter to the antenna. The cable consists of an inner conductor with a diameter of 0.2 mm and an outer conductor with a diameter of 2.0 mm, whose thickness is negligible. If the maximum safe potential difference between the conductors is 2.3 kV, what is the maximum charge density the conductors can carry under this safety constraint? (A) 45 μC (B) 50 μC (C) 55 μC (D) 60μC (E) 65 μC

18. A spreading wave packet increases in width over time due to which principle? (A) Second Law of Thermodynamics (B) Conservation of Energy (C) Relativistic Effect (D) Uncertainty Principle (E) Momentum Conservation

19. A particle moves in a non-conservative field but its total energy remains conserved. What is the likely form of the external force? (A) Constant force (B) Position-dependent (C) Velocity-dependent (D) Perpendicular to displacement (E) Time-dependent

1. Consider the situation shown in the figure, where a baseball player slides to a stop on level ground. Using energy considerations, calculate the distance the 65.0-kg baseball player slides, given that his initial speed is 6.00 m/s and the force of friction against him is a constant 450 N. (A)0.6 m (B)1.6 m (C)2.6 m (D)3.6 m (E)4.6 m

2. The Moon orbits Earth each 27.3 days and it has an average distance of 3.84×108 m from the center of Earth. Calculate the period of an artificial satellite orbiting at an average altitude of 1500 km above Earth's surface. The radius of Earth is 6380 km. (A) 0.57 hr (B) 1.9 hr (C) 5.7 hr (D) 19 hr (E) 57 hr

3. What is the final speed of the roller coaster shown in the figure if it starts from rest at the top of the 20.0 m hill and work done by frictional forces is negligible? The gravitational acceleration on Earth's surface is 9.8 m s-2. (A)2.4 m/s (B) 4.9 m/s (C) 9.8 m/s (D) 19.8 m/s (E) 29.4 m/s

4. The escape velocity (minimum velocity to escape the Earth's gravitational potential) for a 100-kg object on Earth is about 11 km/s. What is the escape velocity of a 50-kg object on the surface of Earth? (A) 11 km/s (B) 22 km/s (C) 5.5 km/s (D) 44 km/s (E) 2.75 km/s

5. At what temperature would helium atoms have an rms speed enough to escape the Earth's gravitational potential? The proton mass is kg. (A) 200 K (B) 600 K (C) 2×103 K (D) 6×103 K (E) 2×104 K

6. Suppose an ice skater is soing at 0.8 revolutions (rev) per second with her arns extended. She has a moment of ineria of 2.34 kg • m2 with her arms extended and of 0.363 kg • m2 with her a close to her body (appropriate for a 60-kg skater). What is her angular velocity in revolutions per second after she pulls in her arms?(A) 2.2 rev/s (B) 3.2 rev/s (C) 4.2 rev/s (D) 5.2 rev/s (E) 6.2 rev/s