Question

A student pushes their backpack across the table. What type of friction is acting against the motion of the backpack 

Answer 1

Kinetic friction.

Step-by-step explanation:

Since the object is moving, it is kinetic friction that is acting against the backpack. You can calculate Friction(force kinetic) by multiplying the coefficient of friction kinetic(based on what you know about the surfaces) with the normal force, which is equal to the force of gravity on a surface(this is calculated by the mass(usually in kg) multiplied by 9.8m/s^2(gravity)).