Question
A target of mass 400 g moving with a horizontal speed of 10 m/s is hit by a bullet of mass 0.01 kg moving in opposite direction. If both the bullet and the target come to rest after the collision, calculate the velocity of the bullet at the time of striking the target.
Solution
Mass of the target, m1 = 400 g = 0.4 kg
Initial velocity of the target, u1 = 10m/s
Final velocity, v1 =0
Mass of the bullet, m2 = 0.01 kg
Initial velocity of the bullet, u2 = ?
Final velocity, v2 =0
According to the law of conservation of momentum,
m1u1 + m2u2 = m1v1 + m2v2
0.4 x 10 + 0.01 x u2 = 0 + 0
Negative sign shows that the bullet is moving in a direction opposite to that of the motion of target.
