Question

A body dropped from a height $h$ with an initial speed zero reaches the ground with a velocity of $3km/h$. Another body of the same mass was dropped from the same height $h$ with an initial speed $4km/h$ will reach the ground with a velocity of

• A. $3km/h$
• B. $4km/h$
• C. $5km/h$
• D. $12km/h$

Answer 1

The correct option is C $5km/h$

Using the third equation of motion,

$v^2=u^2+2as$

For the first case,

$u=0$

$v=\sqrt{2gh}$

$9=2gh$

For the second case,

$v^{\prime 2}=4^2+2gh$

$v^{\prime 2}=25$

$v^{\prime }=5km/h$