Q. A force of $19.6\ N$ when applied parallel to the surface just moves a body of mass $10\ kg$ kept on a horizontal surface. If a $5\ kg$ mass is kept on a horizontal surface. If a $5\ kg$ mass is kept on the first mass, the force applied parallel to the surface to just move the combined body is
A) $29.4\ N$
B) $39.2\ N$
C) $18.6\ N$
D) $42.6\ N$
Explanation
(a) $F_{l} \propto R\ \therefore F_{l} \propto m$ $i.e.$ limiting friction depends upon the mass of body. So,
$\Rightarrow \left( F_{l} \right)^{'} = \frac{3}{2} \times F_{l} = \frac{3}{2} \times 19.6 = 29.4\ N$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.