NDA2026General AbilityGeneral ScienceActual
The position vector of a particle is given by r = 3 ,t^2 i + 2 ,t j + 5 , k . Which one of the following statements is correct?
Options
- AThe force acting on the particle is parallel to the instantaneous momentum of the particle.
- BThe force acting on the particle is perpendicular to the instantaneous momentum of the particle.
- CThe particle experiences zero force.
- DThe force acting on the particle is not parallel to the instantaneous momentum of the particle.
Correct answer
D. The force acting on the particle is not parallel to the instantaneous momentum of the particle.
Step-by-step solution
Given position vector r = 3 t^2 i + 2 t j + 5 k Velocity v = d r dt = 2 3 t i + 2 j Instantaneous momentum p = m v = m(2 3 t i + 2 j ) Acceleration a = d v dt = 2 3 i Force F = m a = 2 3 m i Taking the cross product of force and momentum: F p = (2 3 m i ) m(2 3 t i + 2 j ) = 2 6 m^2 k 0 Since the cross product is non-zero, the force is not parallel to the instantaneous momentum. Also, F p = 12m^2t 0 , so they are not perpendicular either. Answer: The force acting on the particle is not parallel to the instantaneous