Question

A horizontal force F is applied such that the block remains stationary, then which of
the statements is false?
a) f = mg, where f is frictional force
b) F = N, where N is normal force
c) f does not produce any torque
d) N does not produce any torque​

Answer 1

When the horizontal force F is applied such that the block remains stationary, then the statement which is false is a) f = mg, where f is the frictional force.

• For a translatory equilibrium the condition will be Efx = 0 and Efy = 0.
• Where Efx = N - F = F = N and Efy = f - mg = 0 = f = mg.
• On rotational equilibrium Στ=0, thus τ→f+τ→N = 0 and f ≠ 0,  τ→N≠0 and the torque by friction and the normal reaction will be opposite.