When is the rate of change of momentum equals zero ?
Well, if the rate of change of momentum is zero, then the momentum is constant (obviously.) That can mean the momentum p = 0 (ie the velocity is zerozero.) Either way, the impulse of a force is related to the change in momentum, therefore there is no force involved if momentum is zero.
Impulse = FΔt = mΔv
Therefore change in momentum = mΔv/Δt = F
Therefore the force is zero if there is no change in momentum.
Hope this helps.
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