NEET-XII-Physics
P1 year:2019
- #9A disc of radius 2 m and mass 100 kg rolls on
a horizontal floor. Its centre of mass has speed
of 20 cm/s. How much work is needed to stop
it?
(1) 3 J
(2) 30 kJ
(3) 2 J
(4) 1 JdigAnsr: 1Ans : ( 1 )
Sol. Work required = change in kinetic energy
Final KE = 0
Initial KE = ``\frac12 mv^2 + \frac12 I {\omega}^2 = frac34 mv^2``
= ``\frac34 \times 100 \times (20 \times 10^{-2})^2 = 3J ``
|``\triangle `` KE| = 3 J