What is the resultant force on the calculator?

Question

Your professor is trying to show friction by pushing a calculator along a table. The frictional coefficient is k=0.6. The calculator has a mass of 2.5 kg, and your professor is pushing with 50 N of force. What is the resultant force on the calculator?

Answer 1

I'd first draw a free-body diagram here and label all that I can. There are four forces acting on this calculator.

1. Down: F_g = mg, which you should be able to calculate
2. Up: F_normal will be equal and opposite to F_g (because the table is assumed to be level and the calculator has no vertical motion)
3. Sideways:
4. Direction will depend on your diagram, but here there will be an applied force (50 N from your professor) and a frictional force, which will act in the opposite direction to the applied force.
5. The frictional force can be found using F_friction = k * F_normal

The resultant force on the calculator will then simple be F_resultant = F_applied - F_friction