Q.
A man of 50 kg is standing at one end on a boat of length 25 m and mass 200 kg. If he starts running and when he reaches the other end, he has a velocity $2\ {ms}^{- 1}$ with respect to the boat. The final velocity of the boat is ( in ${ms}^{- 1})$
A) $\frac{2}{5}$
B) $\frac{2}{3}$
C) $\frac{8}{5}$
D) $\frac{8}{3}$
Explanation
(a) Let $v$ be the velocity of the boat with respect to the water, then from conservation of linear momentum.
$(200 + 50)v + 50 \times 2 = 50 \times 0 + 200 \times 0$
$250v = - 100$
$v = - \frac{100}{250} = - \frac{2}{5}\ {ms}^{- 1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.