You launch a ball in the air with an initial velocity of 25 m/s. What is the acceleration going up ?
A. 9.81 m/s2
B. - 9.81 m/s2
C. 25 m/s

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