# Finding Force then converting to work

1. Oct 19, 2011

### cjknowland

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

A 1.50 x 10^3 kg car starts from rest and accelerates uniformly to 19.3 m/s in 11.6 s. Assume that air resistance remains constant at 400 N during this time.

(a) Find the average power developed by the engine.

(b) Find the instantaneous power output of the engine at t = 11.6 s, just before the car stops accelerating.

2. Relevant equations

W=F(Δx)
F=ma

3. The attempt at a solution

I used kinematic equations to find the Δx at 111.94 and a at 1.663 m/s. (may want to check)

I then used F=ma to find F = 2495.689

then multiplied F by Δx to get 279367.4267 for Work but I am told by my homework website that I am off by a multiple of ten. I can easily guess for the answer but I want to know where I went wrong...

thank you

2. Oct 19, 2011

### grzz

I do not think there is any mistake in your work. But you were asked for the POWER and you found ONLY the work done up to now.