# A car with a mass of 1920 kg kg starts from rest and accelerates to a speed of 19.8 m/s in 11.3 s. -?

Assume that the force of resistance remains constant at 387.3 N during this time. What is the average power developed by the car’s engine?

Answer in units of W.

### 2 Answers

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- NCSLv 71 month agoFavourite answer
Assuming the acceleration is uniform, the distance covered is

d = ½*19.8m/s * 11.3s = 112 m

total work done = KE + friction work

... = ½ * 1920kg * (19.8m/s)² + 387.3N*112m = 4.20e5 J

avg power P = work / time = 4.20e5J / 11.3s = 3.71e4 W

Hope this helps!

- 1 month ago
I'm not sure but this is what I have so far:

velocity * time = distance

(19.8 m/s)(11.3s) = 223.74 m

force * distance = Work

(387.3 N)(223.74 m) = 86,654.502 (N*m)

N*m = Joule

Watts= Joules/seconds P= work/time

7,668.54 W

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