Question

a) How is the kinetic energy of a moving train affected it its velocity becomes one third?

b) A car and bus are moving with the same speed. which one has more kinetic energy? explain

Answer 1

(1) Since, Kinetic energy is given by :
E = $\frac{1}{2}m{v}^2$ where m and v are the mass and velocity of the body respectively.
Given , v' = $\frac{v}{3}$
So, E ' =$\frac{1}{2}mv{\text{'}}^2$= $\frac{E}{9}$
(2) Since, a bus has more mass than that of a car. Given, velocity of bus = velocity of car.
So, from the above formula, we can say that kinetic energy of bus is more than kinetic energy of car as it is directly proportional to mass of the body.