Question

Calculate the work done (in KJ) required stopping a 1500 kg car, moving at the velocity of 90 km/hr.

Answer 1

Velocity = 90 $\frac{km}{hr}$ = 90 × 5/18 = 25 $\frac{m}{sec}$;

$v_1$ = 25 m/s, $v_2$ = 0

Work done to stop the car = $\frac{1}{2}$ m $v_1^2$ - $\frac{1}{2}$ m $v_2^2$

= $\frac{1}{2}$ × 1500 × ${25}^2$ - 0 = 750 × 625 = 468.75 KJ