# Question on Power

Jo-AnneLi

## Homework Statement

What minimum horsepower must a motor have to be able to drag a 340 kg box along a level floor at a speed of 1.45 m/s if the coefficient of friction is 0.50?

## Homework Equations

Power = Change in Energy/time = Work/time
Change in energy = Final energy - Initial energy
Work = Net Force x displacement
Force of Friction = Normal force x coefficient of friction = mg x coefficient of friction
Kinetic energy = 1/2 x m x v^2
Change in gravitational potential energy = mgh

## The Attempt at a Solution

I know that we should always start with the equation Power = Work/time or Power = Change in energy/time, and then sub in values. The problem is that of the equations given above, none of them seem to work. We are not given displacement. I found the friction force = 1667.7 N but I'm unsure as to how to find net force. Kinetic energy = 357.425 J, but is that the initial/final energy and how do I find the other one?
Welcome to the Physics Forums! 