Q. The velocity of a body of mass $20\ kg$ decreases from $20\ m/s$ to $5\ m/s$ in a distance of $100\ m$. Force on the body is
A) $- 27.5\ N$
B) $- 47.5\ N$
C) $- 37.5\ N$
D) $- 67.5\ N$
Explanation
(c) Here, $m = 20\ kg\ ,\ u = 20\ m/s,\ v = 5m/s,\ s = 100m$
Using $v^{2} = u^{2} + 2as$
$F = ma = m \times \left( \frac{v^{2} - u^{2}}{2s} \right)$
Substituting the values, we get
$F = 20 \times \left\lbrack \frac{(5)^{2} - (20)^{2}}{2 \times 100} \right\rbrack = - 37.5\ N$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.