NEET2013PhysicsRotational MotionActual
The discs are rotating about their axes, normal to the discs and passing through the centres of the discs. Disc D₁ has 2 ~kg mass and 0.2 ~m radius and initial angular velocity of 50 rad s ⁻¹ . Disc D ₂ has 4 ~kg mass, 0.1 ~m radius and initial angular velocity of 200 rad s ⁻¹ . The two discs are brought in contact face to face, with their axes of rotation coincident. The final angular velocity (in rad s⁻¹ ) of the s
Options
- A60
- B100
- C120
- D40
Correct answer
B. 100
Step-by-step solution
M.J. of D ₁ is I ₁= MR ^2 2 = 2(0.2)^2 2 =0.04 ~kg ~m ^2 initial angular velocity of D₁ is ₁=50 rad S ⁻¹ M.J of D ₂ is I ₂= 4 (0.1)^2 2 =0.02 ~kg m₂ initial angular velocity of D ₂ is ₂= 200 and S ⁻¹ . According to the law of conservation of angular moment gathered L₁=L₂ I ₁ ₁+ I ₂ ₂= ( I ₁+ I ₂ ) = l₁ w₁+l₂ w₂ I ₁+1 = (0.04)^2 50+(0.02)^2 200 0.04+0.02 = 2+4 0.06 =100 rads ⁻¹ gathered