Each soccer ball has a mass of 3kg. A soccer player kicks one ball at a velocity of 14m/s, and it strikes a stationary ball. What is the final speed of the first ball if: a. The first ball stops moving after it strikes the second ball.
b. The first ball continues moving after the collision at 1.8m/s in the same direction.

Uranium has two naturally occurring isotopes. 238u has a natural abundance of 99.3% and 235u has an abundance of 0.7%. it is the rarer 235u that is needed for nuclear reactors. the isotopes are separated by forming uranium hexafluoride uf6, which is a gas, then allowing it to diffuse through a series of porous membranes. 235uf6 has a slightly larger rms speed than 238uf6 and diffuses slightly faster. many repetitions of this procedure gradually separate the two isotopes. what is the ratio of the rms speed of 235uf6 to that of 238uf6? express your answer to five significant figures.