Why pendulum made of invar are used in clock?

Why don't you see your reflection in water with waves or repples

Gordon is going for a run through the park, but it is cold outside. the low outside temperature could affect his personal safety.

Amoving electron has kinetic energy k1. after a net amount of work w has been done on it, the electron is moving one-quarter as fast in the opposite direction. (a) find w in terms of k1. (b) does your answer depend on the final direction of the electron's motion?