Question: An object of mass m is attached to light string which passes through a hollow tube. The object is set into rotation in a horizontal circle of radius , 𝑟1.If the string is pulled shortening the radius to 𝑟2,the ratio of new kinetic energy to the original kinetic energy is
(A) \left( \dfrac{r_{2}}{r_{1}}\right)^{2}
(B) \left( \dfrac{r_{1}}{r_{2}}\right) ^{2}
(C) \dfrac{r_{1}}{r_{2}}
(D) \dfrac{r_{2}}{r_{1}}
Answer: Option (A)
Solution:
