Question

4. Hypervelocity bullets used in 0.22 long rifle usually weigh around 2.1 g and can have a speed of 550m/s. What is the magnitude of the momentum ((in kg.m/s) of the bullet?

5. What is the speed (in m/s) for a 75 kg man to match the momentum of the bullet in number 4?

Answer 1

The magnitude of the momentum ((in kg·m/s) of the bullet is

$$p_b=m_bv_b=0.0021·550=1.155\text{ kg}·\text{m/s}.$$

The speed of the an to match the magnitude of the momentum of the bullet is

$$p_b=p_m,\\ m_mv_m=m_bv_b,\\\space\\ v_m=v_b\frac{m_b}{m_m}=0.0154\text{ m/s}.$$