A tennis player pushes the tennis ball with her racquet over a distance of 0.5m. The ball gains (kinetic) energy of 50J. What was the average force during the "serve"?

Aray of light traveling parallel to the principal axis of a concave mirror will be reflected through the mirror's

Which of the following correctly describes what happens when an atomic bomb explodes? small pieces of fissionable material are joined and form a body with a mass greater than the critical mass, the relative number of neutrons escaping decreases, and a chain reaction and explosion result. large pieces of fissionable matter are brought together quickly and form a body with a mass smaller than the critical mass, the relative number of escaping neutrons increases, and a chain reaction and explosion result.

Avoltaic cell converts chemical energy to