COMEDK2015PhysicsRotational Motion
A uniform circular disc of mass 400 ~g and radius 4.0 ~cm is rotated about one of its diameter at an angular speed of 10 rot / s . The kinetic energy of the disc is
Options
- A3.2 10⁻¹ ~J
- B1.6 10⁻³ ~J
- C3.2 10⁻³ ~J
- D6.4 10⁻⁴ ~J
Correct answer
A. 3.2 10⁻¹ ~J
Step-by-step solution
Given, mass of disc, M=400 ~g =0.4 ~kg Radius, R=4 ~cm =4 10⁻² ~m Angular speed, =2 10 =20 rad / s Moment of inertia of disc about its diameter I_ d = 1 4 M R² Kinetic energy of disc aligned &= 1 2 I_ d ² &= 1 2 1 4 M R² ²= 1 8 M R² ² &= 1 8 0.4 (4 10⁻² )² (20 )² &=3.2 10⁻¹ ~J aligned Hence, no option is correct.