Question

A ball is gently dropped from a height of $20m$. If its velocity increases uniformly at the rate of $10m{s}^{-2}$, with what velocity will it strike the ground ?

• A. $20m/s$
• B. $10m/s$
• C. $40m/s$
• D. $15m/s$

Answer 1

Answer: (A)

Step 1: Given data

Initial velocity $u=0m/s$,

Acceleration $g=10m/s^2$,

Height $h=20m$,

Let the final velocity is $v$,

Step 2: Formula used

$v^2=u^2+2gh$

Step 3: Finding the final velocity

Putting all the values

$v^2=0^2+2\times \left(10m/s^2\right)\times 20m=400m^2/s^2$

$\Rightarrow v=\sqrt{400m^2/s^2}=20m/s$

Hence, the velocity before striking the ground is 20 m/s.

Thus, option A is correct.