1. (1 pt) Show from the relativistic velocity transformation equation that if something is moving with velocity c in some direction in one reference frame O', then it is also moving with c in a frame in which O' is moving with speed u in the same direction.

2. (1 pt) A spaceship moving at velocity 0.7c with respect to the earth launches a rocket moving in the same direction at a speed of 0.5c with respect to the spaceship. How fast is the rocket moving with respect to the earth?

3. ( 2pts) A radioactive uranium nucleus (mass 238.0508 amu) can decay to a thorium nucleus (mass 234.0436 amu) and an alpha particle (mass 4.0026 amu) where an amu (atomic mass unit) is equal to 1.661 x 10^-27kg. What is the total kinetic energy of the particles produced in the decay?

4. (2 pts) Light of wavelength 155nm shines on polycrystalline silver (work function = 4.26 eV). What is the maximum kinetic energy of the electrons ejected from the silver?