wiz-icon
MyQuestionIcon
MyQuestionIcon
1
You visited us 1 times! Enjoying our articles? Unlock Full Access!
Question

Two circular discs of moment of inertia 0.4 kg-m2 and 0.6 kg-m2 are rotating about their own axis (vertical axis passing through geometric centre) at the rate of 200 rpm and 50 rpm both in clockwise direction. If both are gently brought in contact to rotate about same axis, the angular speed of the combination is

A
11.5 rad/sec
Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
B
23 rad/sec
No worries! We‘ve got your back. Try BYJU‘S free classes today!
C
0 rad/sec
No worries! We‘ve got your back. Try BYJU‘S free classes today!
D
5.5 rad/sec
No worries! We‘ve got your back. Try BYJU‘S free classes today!
Open in App
Solution

The correct option is A 11.5 rad/sec
Moment of inertia for the discs are:
I1=0.4 kg m2
I2=0.6 kg m2
Frequency of rotation for disc is:
N1=200 rpm, N2=50 rpm
Hence angular speed of the discs about their axis of rotation:
ω1=2πN160=20π3 rad/s
ω2=2πN260=5π3 rad/s
Final moment of inertia I=I1+I2
I=1.0 kg m2
Applying angular momentum conservation on system of discs, since torques of friction is internal and other external torque is absent.
Li=Lf
I1ω1+I2ω2=Iωf ....(i)
Putting the values in eq (i):
(0.4×20π3)+(0.6×5π3)=1×ωf
ωf=11π3=11.5 rad/s

flag
Suggest Corrections
thumbs-up
0
Join BYJU'S Learning Program
similar_icon
Related Videos
thumbnail
lock
Conservation of Angular Momentum
PHYSICS
Watch in App
Join BYJU'S Learning Program
CrossIcon