A billiard ball traveling at 4m/s has an elastic head-on collision with a billiard ball of equal mass that is initially at rest. The first ball is at rest after the collision. What is the speed of the second ball after the collision?

Which statements best describe medical uses for radioactive isotopes? check all that apply. radioactive isotopes are used to detect medical problems. high-energy gamma rays are injected into the body. radioactive isotopes are used to treat some diseases. radiation is used to kill cancer cells. radioactive isotopes are directed at tumors from outside the body.