91Ó°ÊÓ

The momentum$\stackrel{\mathbf{→}}{\mathbf{p}}$of a particle is a vector quantity equal to the product of

the particle’s mass mand velocity$\stackrel{\mathbf{→}}{\mathbf{v}}$ .

$\stackrel{\mathbf{→}}{\mathbf{p}}\mathbf{=}\mathit{m}\stackrel{\mathbf{→}}{\mathbf{v}}$

Newton’ssecond law says that the net force on a particleis equal to the rate of change of the particle’s momentum.

$\underset{\mathbf{}}{\mathbf{∑}}\stackrel{\mathbf{→}}{\mathbf{F}}\mathbf{=}\frac{\stackrel{\mathbf{→}}{\mathbf{d}\mathbf{p}}}{\mathbf{d}\mathbf{t}}$

The momentum of thetruck depends on the velocity since the relative velocity of the truck is different in both the frames, therefore the momentum of the truck is different in both the reference frames.

Since both, the reference frames are not accelerated, so the truck is constantly accelerating in both the reference frames. Therefore, the net force on the truck is the same in both frames. So according to Newton’s Second law rate of change of the truck’s momentum is the same in both the frames.