Question

A horizontal force of 10 newton is necessary to just hold a block stationary against a wall, the coefficient of friction between the lock and the wall 0.2. The weight of block is
A.) 50 N
B.) 100 N
C.) 2 N
D.) 20 N

Answer 1

Hint: For these types of questions we must remember the definition and the formula of the friction and its properties.

Complete step-by-step answer:
Formula Used: ${F_f} = \mu N$

Friction is the force which resists the relative motion of solid surfaces, fluid layers and sliding material elements against each other.

Force acting in a direction parallel to the horizon is known as horizontal force and friction coefficient is defined as the ratio of frictional force between two bodies and the force pressing them together.

Force of friction is given by:

${F_f} = \mu N$
${F_f}$ is the frictional force
$\mu $ is the coefficient of friction
$N$ is the normal force.

As the block is stationary it is in equilibrium.
Hence,

We know, $mg = f$
$mg = \mu N = 0.2 \times 10 = 2N$

Therefore, option C is the correct answer which states that the weight of block is 2N.

Note: From this numerical we can observe that friction force is very important in our everyday life. Hence, we must remember its properties and formula for solving any type of questions quickly and correctly. Also, ${F_f} = \mu N$ is a very important point to remember.