physics30sh
posted by Michael .
a 1000 kg car engine exerts a force of 3000 N while the car accelerates from 20 m/s to 30 m/s is 5.0 seconds. How much force of resistance does the car experience?

in those five seconds, the avg speed was 25m/s, so the distance covered was 125m
3000*125forceresitance*125=change in KEnergy. 
i don't get that at all...

the change of kinetic energy has to equal the work frictonenergy that went into it.