Question

An advertisement claims that a certain $1200kg$ car can accelerate from rest to a speed of $25m/s$ in a time of $8s$. What average power must the motor produce to cause this acceleration? (Ignore friction losses)

Answer 1

The work done in accelerating the car is given by
$W=\Delta K=\frac{1}{2}m(v_f^2-v_i^2)=\frac{1}{2}[1200{\left(25\right)}^2-0]=375kJ$
Power $=\frac{W}{t}=\frac{375}{8}=46.9kW$