a car with a mass of 1.50 x 10^3 kg starts from rest and acceleration to a speed of 18.0 m/s in 12.0 s. Assume that the force of resistance remains constant at 400.0 N during this time. What is the average power developed by the cars engine

Answer 1

M*g = 1500 * 9.8 = 14,700 N. = Wt. of car. = Normal(Fn).

V = Vo + a*t = 18.
0 + a*12 = 18, a = 1.5 m/s^2.
d = 0.5a*t^2 = 0.75*12^2 = 108 m.

Fr = 400 N.

Fe-Fr = M*a.
Fe = M*a+Fr = 2250 + 400 = 2650 N. = Force of engine.

P = Fe*d/t = 2650 * 108/12 = 23,850 J/s = 23,850 Watts.