question_answer

An object of mass m is attached to light string which passess through a hollow tube. The object is set into rotation in a horizontal circle of radius,\[{{r}_{1}}\]. If the string is pulled shortening the radius to\[{{r}_{2}}\], the ratio of new kinetic energy to the original kinetic energy is:

A)  \[{{\left( \frac{{{r}_{2}}}{{{r}_{1}}} \right)}^{2}}\]

B)                         \[{{\left( \frac{{{r}_{1}}}{{{r}_{2}}} \right)}^{2}}\]            

C)         \[\frac{{{r}_{1}}}{{{r}_{2}}}\]                     

D)         \[\frac{{{r}_{2}}}{{{r}_{1}}}\]

E)  1