JEE Main2013PhysicsRotational MotionActual
A particle of mass 2 ~kg is moving such that at time t , its position, in meter, is given by r (t)=5 i -2 t^2 j . The angular momentum of the particle at t=2 s about the origin in kg m ⁻² ~s ⁻¹ is :
Options
- A-80 k
- B(10 i -16 j )
- C-40 k
- D40 k
Correct answer
A. -80 k
Step-by-step solution
Angular momentum L = m ( v r ) aligned & =2 ~kg ( dr dt r )=2 ~kg (4 t 5 i -2 t ^2 j ) & =2 ~kg (-20 t k )=2 ~kg -20 2 ~m ⁻² ~s ⁻¹ k & =-80 k aligned