Question

bullet of mass 0.04 kg moving north with an initial velocity of 700 m/s is subjected to a force of 7 N North for 3.5 s. Calculate the final velocity of the bullet

Answer 1

If the bullet is moving North and the force acts North too, this force will accelerate the bullet.

According to momentum conservation, we have:

$$p_i+\Delta p=p_f$$

In this equation,

$$\Delta p=Ft,\\ p_i=mv_i,\\ p_f=mv_f.$$

Therefore:

$$mv_i+Ft=mv_f,\\\space\\ v_f=v_i+\frac{Ft}{m}=1312.\text{ m/s}.$$