Consider a block of mass `10 kg`. which rests on as smooth surface and is subjected to a horizontal force of `6N`. If observer `A` is in a fixed frame `x`.

Options

A. The final speed of the block in `4s` is `7.4m//s` if it has an initial speed of `5m//s` measured from the fixed frame.
B. The same speed will be observed by observer `B` Attached to the `x` axis that moves at a constant velocity of `2m//s` relative to `A`.
C. Principle of impulse and momentum is valid for observers in an inertial reference frame.
D. Momentum of a body is reference frame dependent.

Answer

B, D

Explanation

Impulse `=` Change in momentum
`implies 6xx4=10(v-5)implies v=7.4m//s`
With respect to observer B, speed will be `v-2=7.4-2=5.4m//s`