Concepts Of Physics MCQ Edition [Volume 1]PhysicsWork and Energy
The kinetic energy of a particle increases continuously over time.
Options
- AThe magnitude of its linear momentum increases continuously.
- BThe resultant force on the particle must always form an angle of less than 90^ with the velocity.
- CIts height above ground level must continuously decrease.
- DThe resultant force on the particle must be parallel to its velocity at all instants.
Correct answer
B. The resultant force on the particle must always form an angle of less than 90^ with the velocity.
Step-by-step solution
The kinetic energy of a particle is given by K = p^2 2m . Since the kinetic energy increases continuously, the magnitude of its linear momentum p must also increase continuously. The rate of change of kinetic energy is equal to the power delivered by the net force, which is given by dK dt = F v = F v . For the kinetic energy to increase continuously, dK dt > 0 , which implies > 0 . Thus, the angle between the resultant force and the velocity must always be less than 90^ . The height of the particle does not necessa