Question

a stone is dropped vertically into a lake which one of the following statements best describes the motion of the stone at the instant it enters the water?a)Its velocity and acceleration are both downwards b)It has an upwards velocity and a downward acceleration c)Its velocity and acceleration are both upwards d)It has a downward velocity and an upward acceleration

Answer 1

the instant it hits the water, it slows down, due to the force of friction at impact. That upward force reduces speed, thus a negative accleration (ie, upward acceleration).