Question

A ball is launched from the ground with a horizontal speed of 30 m/s and a vertical speed of 30 m/s. When will the ball hit the ground again? OA. 4s B. 5 s OC. 6 s D. 3 s ​

Answer 1

C. 6 s

Step-by-step explanation:

The kinetic energy of the ball in the vertical direction is converted to potential energy at the top of its flight, and back to the same amount of kinetic energy when it hits the ground.

The velocity changes from +30 m/s vertically to -30 m/s vertically. The time required for that velocity change is ...

t = Δv/g . . . . . where g is the acceleration due to gravity

t = ((-30 m/s) -(30 m/s))/(-9.8 m/s²) ≈ 6.122 s

The flight time of the ball is about 6 seconds.