Question
Question: A boy of mass 50 kg produces an acceleration of 2m/s<sup>2</sup> in a block of mass 20kg by pushing ...
A boy of mass 50 kg produces an acceleration of 2m/s2 in a block of mass 20kg by pushing it in horizontal direction. If the boy moves with the block without sliding, then the friction force exerted by the surface on the boy is equal to:
A
180 N
B
140 N
C
100 N
D
70 N
Answer
140 N
Explanation
Solution
For Block F = 20.2 = 40 N
As man exerts 40 N force on block, block exerts 40N force on the boy, in opposite direction. The boy is also moving with same acceleration. If f is friction force exerted by the surface on the boy then
f – 40 = 50.2
f = 140 N.