Question

The rear side of a truck is open and a box of mass $20\text{kg}$ is placed on the truck $4\text{m}$ away from the open end, $\mu =0.15$ and $g=10{\text{m/sec}}^2$. The truck starts from rest with an acceleration of $2{\text{m/sec}}^2$ on a straight road. The distance moved by the truck when box starts fall down.

• A. $4\text{m}$
• B. $8\text{m}$
• C. $16\text{m}$
• D. $32\text{m}$

Answer 1

The correct option is C $16\text{m}$

Acceleration of box w.r.t. truck
$=\frac{ma-\mu mg}{m}=2-\left(0.15\right)\left(10\right)=0.5{\text{ms}}^{-2}$
The box will fall off at time $t,$
then from
$s=ut+\frac{1}{2}a{t}^2;4=\frac{1}{2}\left(0.5\right)t^2\Rightarrow t=4\text{s}$
Distance travelled by truck during this time is $=\frac{1}{2}\left(2\right)(4{)}^2=16\text{m}$