Question

In which of the following cases forces are not required. To keep the:

• A. particle going in a circle
• B. particle going along a straight line
• C. momentum of the particle is constant
• D. acceleration of the particle is constant

Answer 1

Answer: (C)

momentum of the particle is constant

Force is the rate of change in momentum,

$F=\frac{dP}{dt}$where P is momentum $P=mv$

If the rate of change in momentum is zero or momentum is constant then net force acting on the body is zero

$F=\frac{dp}{dt}=0$ when P is constant or $zero$