Question

What is the work done (in KJ) to increase the velocity of a car from 36 $\frac{km}{hr}$ to 90 $\frac{km}{hr}$? When the weight of the car is 1000 kg.

Answer 1

Given,

Final velocity, $v_2$ = 90 * $\frac{5}{18}$ = 25 $\frac{m}{sec}$,

Initial velocity, $v_1$ = 36 * $\frac{5}{18}$ = 10$\frac{m}{sec}$

Work done to increase the velocity will be the change in kinetic energy.

$W=\Delta KE=K{E}_f-K{E}_i=\frac{1}{2}$ m ${v_2}^2$ - $\frac{1}{2}$ m ${v_1}^2$

$W=({25}^2$ - ${10}^2)\times \frac{1000}{2}$

$W=500\times (625-100)=500\times 525=262.5$ KJ.