Question

A 250g bullet moving at 330m/s hits and travels through a 1.2 kg block of wood, 0.30 m long. If the bullet's speed upon leaving the block is 120 m/s, find...
a) the impulse applied to the block
b) the impulse applied to the bullet
c) the time the bullet spent in the wood
d) the force applied to the bullet

Answer 1

A 250g bullet moving at 330m/s hits and travels through a 1.2 kg block of wood, 0.30 m long. If the bullet's speed upon leaving the block is 120 m/s, find...

a) the impulse applied to the block

b) the impulse applied to the bullet

c) the time the bullet spent in the wood

d) the force applied to the bullet

Solution:

a) the impulse applied to the block = $MV = m(V_f - V_i) = 0.25 \times (330 - 120) = 52,5 \frac{kg \ m}{s}$

b) the impulse applied to the bullet = $m(V_f - V_i) = 0.25 \times (330 - 120) = 52,5 \frac{kg \ m}{s}$

d) the force applied to the bullet

$$F_l = \frac{m V_f^2}{2} - \frac{m V_i^2}{2} = 0.25 \times 0.5 \times (330^2 - 120^2) = 11812,5 \ J \gg F = 39375 \ N$$

c) the time period the bullet spent in the wood

$$F_t = m(V_f - V_i) = 0.25 \times (330 - 120) = 52,5 \frac{kg \ m}{s} \gg t = 0,00133 \ s \approx 1 \ ms$$