Question

A boy having a mass of $60kg$, holds in hand a school bag of weight $40N$. With what force the floor will push up on his feet ? $\left(g=10m/s^2\right)$

• A. 100 N
• B. 600 N
• C. 640 N
• D. 64 N

Answer 1

Answer: (C)

Total force acting on boy bag system, is given by

$F=$ weight of boy $+$ weight of bag
$F=60g+40N$
$\Rightarrow F=60\times 10+40=640N$
From Newton's third law, to every action there is an equal and opposite reaction.
Therefore, the floor will push on his feet with a force of $640N$.