Question

The speed of a car of mass 500 kg increases from 36 km/h to 72 km/h . Calculate the increase in its kinetic energy.

• A. $7.5\times {10}^{5}J$
• B. $5.5\times {10}^{4}J$
• C. $7.5\times {10}^{3}J$
• D. $7.5\times {10}^{4}J$

Answer 1

The correct option is D $7.5\times {10}^{4}J$

Initial speed $u=36km/h=10m/s$

Final speed $v=72km/h=20m/s$

Now change in KE=$\frac{m{v}^2}{2}-\frac{m{u}^2}{2}$

change in KE=$\frac{500\times {20}^2}{2}-\frac{500\times {10}^2}{2}$

$\Delta KE=7.5\times {10}^{4}J$