A 100 N force presses a 3 kg block against a vertical wall at 30° as shown. The coefficient of friction is 1/4. Find the frictional force in N.

Question

G1 Physics · Accepted Answer

The applied force has upward component 100 sin30°=50 N, while weight is 30 N. The block tends upward by 20 N, so friction acts downward with magnitude 20 N.