Question

A block rests on a long plank that is moving with a constant velocity $2.0$ m/s on a horizontal floor. Coefficient of friction between the block and the plank is $0.10$. If the plank starts decelerating uniformly and stops in $0.50$s, what is the distance slid by the block on the plank? Acceleration of free fall is $10m/s^2$.

• A. $0.50$m
• B. $0.75$m
• C. $1.0$m
• D. $1.25$m

Answer 1

The correct option is D $1.25$m

$V_{plank}=0$

$u_{plank}+at=0$

$2-a_r.0.5=0$

$a_r=4m/s^2$

If we apply relative concept, $a_{net}=a_r-ug$

$4-1=3m/s^2$

$s=\frac{1}{2}\times a\times (0.5{)}^2$

$s=1.25$