Question

9. A truck of mass 1000 kg, increases its speed from 36 km h-1 to 72 km h-1. Find the increase in its kinetic energy Ans. 1-5 x 105 J ​

Answer 1

mass of the truck=1000kg

Initial speed,u=36 km/hr

So,we have to convert them into metre/seconds

so,now u=36×1000/3600=10m/s

Final speed,v=72 km/hr

so,now again convert them into m/s

so,now v=72×1000/3600=20 m/s

Now, Increase In Kinetic Energy

$= \frac{1}{2} m {v}^{2} - \frac{1}{2} m {u}^{2}$

$= \frac{1}{2} m( {v}^{2} - {u}^{2} )$

$= \frac{1}{2} \times 1000( {20}^{2} - {10}^{2} )$

$1.5 \times {10}^{5} J$

hope it helps you dear!!!....