Which equation correctly relates kinetic energy, mass, and velocity?

which of the following is an example of kinetic energy?
a boy resting on a park bench
a book sitting on a shelf
a rubber band stretched as far as it can go
a swing moving back and forth

What is relative velocity? in which condition is relative velocity known by adding the velocity of the first body and that of the second body

At very high pressures, gases become and will eventually a) more dense; become hotter b) more dense; change to a liquid or solid c) less dense; combust d) less dense; turn into a liquid

Which statement best describes the superposition principle? a.) if two in-phase waves arrive simultaneously at a point, their amplitudes add up b.) if two out-of-phase waves arrive simultaneously at a point, their amplitudes add up c.) if two in-phase waves arrive at a point one after another, their amplitudes add up d.) if two out-of-phase waves arrive at a point one after another, their amplitudes adds up