Posted by **Heart** on Wednesday, December 23, 2009 at 9:23pm.

A race car has a mass of 710 kg. It starts from rest and travels 40.0 m in 3.0 s. The car is uniformly accelerated during the entire time. What net force is exerted on it?

- physics =) -
**MathMate**, Wednesday, December 23, 2009 at 9:34pm
First calculate the acceleration from the distance and time using the formula:

S=v0t+(1/2)at²

where

a=acceleration

S=distance

v0=initial velocity

t=time

a=2(S-v0t)/t² (assumed uniform)

Find force F from

F=ma

- physics =) -
**Heart**, Wednesday, December 23, 2009 at 9:38pm
Thanks a lot! I got F = 6311.11 N.

- physics :) -
**MathMate**, Thursday, December 24, 2009 at 7:41am
The answer is correct!

Have a merry Christmas, and enjoy your holidays!

- physics =) -
**drwls**, Thursday, December 24, 2009 at 8:17am
F*X = KE increase = (1/2) M Vfinal^2

Vfinal = 2*Vaverage = 2*X/T =2*(40/3) = 26.67 m/s

F = (1/2)*(710)*(26.67)^2/40 = 6313 N

We agree

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