A force of 40 N acts on a particle of mass 8 kg which is at rest. How far will the particle move in 4 seconds? A) 40 m B) 60 m C) 10 m D) 32 m

What you are given and what you need

You know the force, the mass, and that the particle starts from rest. The job is to find how far it travels after a time, assuming the force (and so the acceleration) stays constant.

Convert force into acceleration (Newton's second law)

Use Newton's second law: $$F = ma$$ So, $$a = \frac{F}{m} = \frac{40}{8} = 5\,\text{m/s}^2$$

Use constant-acceleration motion from rest

Since it starts from rest, $u = 0$. Use $$s = ut + \tfrac12 a t^2$$ Substitute $u=0$, $a=5$, $t=4$: $$s = 0\cdot 4 + \tfrac12(5)(4^2) = \tfrac12\cdot 5 \cdot 16 = 40\,\text{m}$$

Match to the multiple-choice options

$40\,\text{m}$ corresponds to A) 40 m.