NTA Abhyas JEE Main2020PhysicsRotational MotionPractice
The toy-top (initially at rest) shown in the figure, has a moment of inertia 4 × 10 - 4 kg m 2 and it is free to rotate about the stationary axis A A ' . The string wrapped around the peg of the toy-top is pulled outwards without letting it slip and simultaneously maintaining a constant tension of 5 . 625 N . If ω is the angular speed (in rad s - 1 ) of the top after 80 cm of string has been pulled off the peg, then
Correct answer
1.50
Step-by-step solution
Work done = F × Δ r = 5.625 × 0.8 m = 4.5 J and work done = Δ K = 1 2 Iω r 2 − 1 2 Iω 1 2 ∴ 4.5 = 1 2 × 4 × 10 − 4 × ω r 2 − 0 ... ( ∵ top starts from rest, ω i = 0 ) ω f = 150 rad/s