A rock is thrown from ground level at some angle above the horizontal with a certain velocity. It reaches its highest point and starts falling down. What is the magnitude of the velocity of the rock right before it hits the ground?
A) It is equal to its initial vertical velocity.
B) It is equal to its initial horizontal velocity.
C) It is equal to the magnitude of its initial velocity.
D) 0
E) Cannot be determined without additional information.

Question

Quizplus · Accepted Answer

The velocity of the rock right before it hits the ground is equal to the magnitude of its initial velocity because the force of gravity causes the rock to accelerate downwards and gain speed, but there is no force acting on it in the horizontal direction to change its horizontal velocity. Therefore, the magnitude of the velocity remains constant throughout the motion of the rock.

A Rock Is Thrown from Ground Level at Some Angle