Question

A ball dropped freely takes $0.2s$ to travel the last $6m$ distance before hitting the ground. Total time of fall is $(g=10m{s}^{-2})$:

• A. $2.9s$
• B. $3.1s$
• C. $2.7s$
• D. $0.2s$

Answer 1

The correct option is B $3.1s$

Let $T=$ total time taken in second
$S=$ total distance traveled in meter
$V=$ velocity of particle in m/sec
So in this question the condition is of free fall so acceleration of the particle will remain constant through out the process.
$T=T_1+T_2$
$S=S_1+S_2$
Given that: $T_1=0.2s$ and $S_1=6m$

Thus, $6=u\left(0.2\right)+\frac{1}{2}10(0.2{)}^2$

Thus, we get $u=29m/s$

Now using:
$u=0+gt$(as the ball is dropped with initial velocity as zero)

$t=\frac{29}{10}=2.9s$

Thus we get total time as $2.9+0.2=3.1s$