AP EAMCET202022 Sep 2020Evening ShiftPhysicsRotational MotionActual
A 20 ~kg flywheel in the form of a uniform circular disc, 1 ~m in diameter is making 120 rpm . What is its angular momentum?
Options
- A3.14 ~kg ~m ^2 ~s ⁻¹
- B31.4 ~kg ~m ^2 ~s ⁻¹
- C314 ~kg ~m ^2 ~s ⁻¹
- D0.314 ~kg ~m ^2 ~s ⁻¹
Correct answer
B. 31.4 ~kg ~m ^2 ~s ⁻¹
Step-by-step solution
Mass of fly wheel, m=20 ~kg Diameter, D=1 ~m Radius, R= 1 2 =0.5 ~m Angular velocity, =2 120 60 =4 rad s ⁻¹ Moment of inertia of uniform circular disc, aligned I & = m R^2 2 = 20 (0.5)^2 2 & =10 0.25 & =2.5 ~kg - m ^2 aligned Angular momentum, aligned L & =I & =2.5 4 & =2.5 4 3.14 & =31.4 ~kg ~m ^2 ~s ⁻¹ aligned