Rotational MotionHard
Question
A small mass attached to a string rotates on a frictionless table top as shown. If thetenstion in the string is increased by pulling the string causing the radius of the circularmotion to decreases by factor of 2, the kineticenergy of the mass will
Options
A.decrease by a factor of 2
B.remains constant
C.increase by a factor 2
D.increase by a factor 4
Solution
Accordingh to law of conservation of angular momentum
mv r = mv′ r′
vr = v′
v′ = 2v .......(i)
∴
or
[Using (i)]
K′ = 4K.
mv r = mv′ r′
vr = v′
v′ = 2v .......(i)
∴
or
[Using (i)]K′ = 4K.
Create a free account to view solution
View Solution FreeMore Rotational Motion Questions
A bicycle is in motion. The force of friction exerted by the ground on its wheel is such that it acts :...Proton, Deuteron and alpha particle of the samekinetic energy are moving in circulartrajectories in a constant magnetic ...Three thin uniform rods each of mass M and length L are placed along the three axis of a cartesian coordinate system wit...Off two eggs which have identical sizes, shapes and weights, one is raw and the other is half-boiled. The ratio between ...A boy stands over the centre of a horizontal platform which is rotating freely with a speed of 2 revolution/s about a ve...