Question

a block of mass 10kg is kept at rest on a horizontal surface. find the normal reaction and the limiting friction that can come into play if coefficient of static friction is 0.2. what is the frictional force if a horizontal force of 5N is applied on the block?

Answer 1

Dear Student,

Weight of the body: 100 N

Normal reaction force= 100 N

Now frictiional force is defined as a force which opposses motion. Now since net force acting on the body is zero, hence there is no fricitonal force acting.

Maximum value of friction force= coeff. of friction x normal force = 0.2 x 100 = 20 N

Friction force adjust itself to oppose the applied external force which is trying to bring motion to the body. But this is limited to its maximum possible value that is its limiting or threshold value. For cases where applied force is less than threshold value of friction, static friction adjust itself just enough to prevent the body from moving.

Hence in the case where applied force is 5 N, friction force acting on the body is 5 N aswell and as such the body is at rest.

Regards.