Question

11. If a ball with an original velocity of zero is dropped from a tall structure and takes 7 seconds to hit the ground, what velocity does the ball have when it reaches the ground? A. 34.3 m/s B. 156.8 m/s C. 240.1 m/s D. 68.6 m/s

Answer 1

D) 68.6 m/s

Final Velocity = Initial Velocity - (Gravity)(Time)

Final Velocity = 0 m/s - (-9.8 m/s)(7s)

Final velocity = 68.6 m/s

Answer 2

Answer: The correct answer is D) 68.6 m/s

Calculation-

As per the question, the initial velocity of the ball, u = 0

Time take to hit the ground, t = 7 seconds

Here, the acceleration of the ball is the acceleration due to gravity.

Hence, acceleration, a = g =
`9.8\ m/s^2`

The final velocity of the ball just before hitting the ground is calculated as-

V = u+ at

Putting the values in the equation, we get-

V = 0 + gt

= 9.8 × 7 m/s.

= 68.6 m/s

Thus, ball has the velocity of 68.6 m/s when it reaches the ground.