# Work Energy Power Problem?

1. May 7, 2012

### BEANTOWN

1. The problem statement, all variables and given/known data

A 5.0 kg box is sliding across the floor at 2.0 m/s when it is accelerated to 8.00 m/s in 1.8 s. If the coefficient of friction is .220 how much power is required to accelerate the box?

m = 5.0 kg vi= 2.0 m/s vf = 8.00 m/s change in time = 1.8 s coefficient = .22

2. Relevant equations

Power = Work (W) / change in time (t)
W= Fnetd

Fnet = ma
3. The attempt at a solution
P= w/ t

w= FNetd

Heres my issue. I know Fnet(net force) = ma, which i can easily calculate. The problem is where do i use the coefficient of friction they gave me. Do I need to use it, if i already have Fnet?

2. May 7, 2012

### Matt4936

You find the force acting against the box and take that away from the force required to accelerate the box to get the net force.

Last edited: May 7, 2012
3. May 7, 2012

### BEANTOWN

So what do i use for the w= Fnetd calculation?

4. May 7, 2012

### Matt4936

F(net)=F(applied)-F(friction)
D= distance the box moved after acceleration