A crate of books rests on a level floor. To move it along the floor at a constant velocity, why do you exert less force if you pull it at an angle Ï above the horizontal than if you push it at the same angle below the horizontal?

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