A truck moving at `15m//s` has KE of `4.2xx10^5` J (a) what is the mass of the truck ? (b) By what multiplicative factor does the kinetic energy of the truck increases if its speed is doubled?

Explanation

(a) `K = (1)/(2) m upsilon^2, m = (2K)/(upsilon^2) = (24.2xx10^5J)/((15m^2) )= 3733 kg`
(b) Kinetic energy depends on the speed squared, and hence doubling the speed increases the
kinetic energy by a factor of four.