Answer
$ 3\times 10^{5}\ J$
Work Step by Step
Given
The mass of the car $m=1500\ kg$
Initial speed of the car $v_i=0\ km/h$
Final speed of the car $v_f =72\ km/h$
We convert given speed to m/s i,e 1 km =1000 m and 1 h = 3600 s;
$v_f = 72\times \frac{1000\ m}{3600\ s}$
$v_f =20\ m/s$
We know that the time interval $t =30\ s$.
Therefore, Kinetic energy at the end of 30 s is
$KE = \frac{1}{2} m v_f^2$
$KE = \frac{1}{2}\times 1500\ kg\times (20\ m/s)^2$
$kE = 3\times 10^{5}\ J$
