A ball is projected upward at time t = 0.0 s,from a point on a roof 90 m above the ground.The ball rises,then falls and strikes the ground.The initial velocity of the ball is 80.5 m/s.Consider all quantities as positive in the upward direction.The velocity of the ball when it is 89 m above the ground is closest to:
A)- 81 m/s
B)- 64 m/s
C)- 48 m/s
D)- 32 m/s
E)- 97 m/s

Question

Quizplus · Accepted Answer

Explanation:The velocity of the ball when it is 89 m above the ground is closest to -81 m/s. This is because the ball is moving upward at a speed of 80.5 m/s when it is projected, and it will continue to move upward until it reaches its maximum height. At its maximum height, the ball will have a velocity of 0 m/s, and it will then begin to fall back to the ground. As it falls, its velocity will increase until it reaches the ground, at which point it will have a velocity of -80.5 m/s.

A Ball Is Projected Upward at Time T = 0