# A Boy of Mass M Is Applying a Horizontal Force to Slide a Box of Mass M' on a Rough Horizontal Surface. the Coefficient of Friction Between the Shoes of the Boy and the Floor Is μ and that - Physics

MCQ

A boy of mass M is applying a horizontal force to slide a box of mass M' on a rough horizontal surface. The coefficient of friction between the shoes of the boy and the floor is μ and that between the box and the floor is μ'. In which of the following cases it is certainly not possible to slide the box?

#### Options

• μ < μ', M < M'

• μ > μ', M < M'

• μ < μ', M > M'

• μ > μ', M > M'

#### Solution

μ < μ', M < M'
Let T be the force applied by the boy on the block.

Free body diagram for the box:

The condition for preventing the slide is
fmax > T
μ'M'g > T         (i)
Now see the free body diagram of a boy of mass M:

fmax = μmg
The condition for preventing the slide is
fmax > T
μmg > T
The condition for sliding the entire system (block and boy) is
f' > f (block is not slide)
μ'M'g > μmg
μ'M' > μm
μ < μ'
m < M'

Is there an error in this question or solution?

#### APPEARS IN

HC Verma Class 11, 12 Concepts of Physics 1
Chapter 6 Friction
MCQ | Q 10 | Page 96