NEET Solved Paper 2017 Question 30
Question: Two discs of same moment of inertia rotating about their regular axis passing through centre and perpendicular to the plane of disc with angular velocities $ {\omega_1} $ and $ {\omega_2}. $ They are brought into contact face to face coinciding the axis of rotation. The expression for loss of energy during this process is
Options:
A) $ \frac{l}{8}{{({\omega_1}-{\omega_2})}^{2}} $
B) $ \frac{1}{2}l{{({\omega_1}+{\omega_2})}^{2}} $
C) $ \frac{1}{4}l{{({\omega_1}-{\omega_2})}^{2}} $
D) $ l{{({\omega_1}-{\omega_2})}^{2}} $
Show Answer
Answer:
Correct Answer: C
Solution:
- $ \Delta KE=\frac{1}{2}\frac{l _1l _2}{l _1+l _2}{{({\omega_1}-{\omega_2})}^{2}} $ $ =\frac{1}{2}\frac{l^{2}}{(2l)}{{({\omega_1}-{\omega_2})}^{2}} $ $ =\frac{1}{4}l{{({\omega_1}-{\omega_2})}^{2}} $
