A box is placed on rough surface.it has a normal force of magnitude 120N.a force of 20N applied to the right cannot move the box.calculate the magnitude and direction of the friction forces

3 answers

If the box cannot move but has a force applied to the right, the force of the friction must be the exact same force but in the opposite direction.
A.K.A. Newtons third law of motion.
Ff =UsN
Ff=(120)(20)
Ff=2400N