another box has a normal force of 100 N acting on it. You start dragging the box across the floor with horizontal force. The coefficient of kinetic friction between the box and the floor is 0.3. Whta is the force of friction on the box?

The force of friction on the box is 30 N

Explanation:

In order to obtain the force of friction, you have to apply the formula of the force of kinetic friction (because the box is moving)

Let Fk represents the force of kinetic friction:

Fk = μN

where μ is the coefficient of kinetic friction and N is the normal force (which is the contact force that the floor applies to the box)

In this case μ=0.3 and N=100N

Replacing in the formula:

Fk = (0.3) (100) = 30 N

Assuming the box moves to the right, the direction of Fk is opposed to the movement. Therefore:

Fk = 30 (-i) N

Where i is the unit vector in the x direction.