a small mass attached to a string rotates on a frictionless table top if the tension in the string is - Physics -

Question

a small mass attached to a string rotates on a frictionless table
top if the tension in the string is increased by pulling the string
causing the radius of the circular motion to decrease by a factor
of 2,the kinetic energy of mass will?

Vikas · Accepted Answer

as we know mvr = constant mvr=mv' 
r2v' = 2vtherefore new kinetic energy is K
E'=12m(2v)2K E= 4×K
Eso kinetic energy will become 4 times

a small mass attached to a string rotates on a frictionless table top if the tension in the string is increased by pulling the string causing the radius of the circular motion to decrease by a factor of 2,the kinetic energy of mass will?