A long spring, when stretched by a distance $$x$$, has potential energy $$U$$. On increasing the stretching to $$n x$$, the potential energy of the spring will be

If reaction is $$\mathrm{R}$$ and coefficient of friction is $$\mu$$, what is work done against friction in moving a body by distance $$\mathrm{d}$$ ?

If kinetic energy of a body is increased by 300%, then percentage change in momentum will be

A particle of mass $$m$$ is moving in a horizontal circle of radius $$r$$ under a centripetal force given by $$\left(\frac{-K}{r^2}\right)$$, where $$K$$ is a constant. Then