A particle is tied to the end of a string of length 20 cm and makes 5 rps. How many revolutions will it make in one second when the string is shortened to 10 cm ?

A particle is tied to the end of a string of length 20 cm and makes 5

1.	A particle is tied to the end of a string of length 20 cm and makes 5 rps. How many revolutions will it make in one second when the string is shortened to 10 cm ?
Answer» Solution :Using the law of conservation of ANGULAR momentum. `I_(1) omega_(1) = I_(2) omega_(2)` `I_(1) = mr_(1)^(2), I_(2) = mr_(2)^(2)` `omega_(1) = 2pi n_(1), omega_(2) = 2pi n_(2)` `mr_(1)^(2) xx 2pi n_(1) = mr_(2)^(2) xx 2pi n_(2), n_(2) = (r_(1)^(2)n_(1))/(r_(2)^(2)) = (20^(3) xx 5)/10^(2) = 2` rps