Question

A block is in limiting equilibrium on a rough horizontal surface. If the net contact force is
normal force, the frictional force is (if N is normal reaction)

Answer 1

Answer:

equal to external force .

Explanation:

for an object to remain in equilibrium/rest , the net external forces must be 0 .

in the above case , Normal reaction force is equal to Mg ,

so the friction force must be counteracted by the external force . The object is in equilibrium, hence friction force will be equal to the external force.