NTA Abhyas JEE Main2020PhysicsLaws of MotionPractice
A body of mass 1 kg starts moving from rest at t = 0 , in a circular path of radius 8 m . Its kinetic energy varies as a function of times as KE = 2 t 2 Joules, where t is in seconds. Then
Options
- ATangential acceleration = 4   m   s - 2
- BPower of all forces at t   =   2   s is 8   W
- CFirst-round is completed in 2   s .
- DTangential force at t   =   2   s is 4   N .
Correct answer
B. Power of all forces at t   =   2   s is 8   W
Step-by-step solution
1 2 m v 2 = 2 t 2 v 2 = 4 t 2    ⇒   v = 2 t a t = d v d t       ⇒      a t = 2   m s - 2 F t = m a t       ⇒       F t = 2   N Power will be inverted only by tangential force P = F → t + F → c . V → since F c ⊥ V  &  F t V P = F t V         ⇒   &#