A truck weighing 1000 kg changes its speed from 36 km h¹ to 72 km h^–1 in 2 minute. Calculate the work done and power spent.

Two identical balls each of mass 4kg are moving towards each other with speeds 2 ms^–1 and 3 ms^–1 respectively. They undergo head on perfectly elastic collision. Then impulse imparted by one ball on other is

A running man has half the kinetic energy that a boy half his mass has. The man speeds up by 1.0ms^–1 and then has the same energy as the boy. What were the original speed of the man and the boy?

State and prove the law of conservation of energy in case of a freely falling body

One end of a spring of natural length h and spring constant k is fixed at the ground and the other is fitted with a smooth ring of mass m which is allowed to slide on a horizontal rod fixed at a height h. Initially, the spring makes an angle of 37° with the vertical when the system is released from rest. The speed of the ring when the spring becomes vertical is