posted by natasha .
A 1000kg car accelerates from rest to 30m/s over a distance of 20m.
a) ignoring friction and air resistance, what is the power generated by the motor?
b) if the friction and air resistance is 200N, what is the power generated by the motor?
a) Power = (Kinetic energy increase)/(time)
Time*Average speed = t*Vfinal/2 = 20 m
Time = 1.333 seconds
Power = (1/2) M Vfinal^2/1.333= 3.376*10^5 J
= 453 Hp
b) Add 200N*20m = 4000J to the KE increase, and divide by 1.333 s
The new answer is 3.406*10^5 J = 457 Hp