Question

A ball is thrown vertically upward from a height of 40 m and hits the ground with a speed that is three times its initial speed. What is the time taken (in sec) for the fall?

a) 2
b) 3
c) 4
d) 5

Answer 1

The time taken for the fall of the ball is 0 seconds, meaning the ball hits the ground instantaneously.

Step-by-step explanation:

To calculate the time taken for the fall, we need to consider the motion of the ball. The initial vertical velocity of the ball is zero, as it is thrown vertically upward. The final vertical velocity of the ball when it hits the ground is three times the initial vertical velocity. Using the equation v = u + gt, where v is the final velocity, u is the initial velocity, g is the acceleration due to gravity, and t is the time taken, we can solve for t.

Given that the initial vertical velocity is 0 and the final vertical velocity is 3 times the initial vertical velocity, we have:

3u = -g*t

Solving for t, we get:

t = -3u/g

Substituting the known values, u = 0 m/s (initial vertical velocity) and g = 9.8 m/s² (acceleration due to gravity), we get:

t = -3*0 / 9.8

t = 0 seconds

Therefore, the time taken for the fall of the ball is 0 seconds, which means the ball hits the ground instantaneously.