Average Power delivered to Engine

[davidatwayne]

Homework Statement

A 1000 kg car, starting from rest, accelerates uniformly to 15 m/s in ten seconds. Assume air resistance is constant at 300N. What is the average power delivered by the engine?

Answers
a. 13500 W
b.18000 W
c. 23000 W
d. 27000 W

Homework Equations

Average power = work/time
work = force(x) where x is magnitude of displacement.
force= mass x acceleration

The Attempt at a Solution

the force is equal to 1000 kg x 15 m/s = 15000

I don't know how to factor in air resistance, or arrive at a final answer. The answer is A...

 

[6Stang7]

explain how you got the force of the car again...

 

[davidatwayne]

force = mass times acceleration
1000 x 15= 15000

 

[6Stang7]

what is the units of the 15 value though

 

[davidatwayne]

ok... i think i got it... after getting the correct force (and units) times the displacement of x, (1800 * 75)/10... gives the correct answer.

thanks.