Question

A truck of mass 2000 kg encounters a constant frictional force of 800 N as it moves on a straight road. The speed of the truck increases from 20 ms−1 to 30 ms−1 as it covers a distance of 400 m. What is the thrust generated by the truck’s engine?

Answer 1

Energy of truck=lost energy due to friction  + K.E. gain

Kinetic enery can be calculated using formula,

K.E = ½ m vsquare

In this case, as speed of the truck increases from 20 ms−1 to 30 ms−1.  

So, Vsquare = (30*30 – 20*20)  

By using frictional force of 800N to cover 400 m distance, we can calculate Wf.