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07/01/2021 11:36 am
Topic starter
A bullet of mass 20 g is horizontally fired with a velocity 150 m/s from a pistol of mass 2 kg. What is the recoil velocity of the pistol?
1 Answer
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07/01/2021 11:43 am
Bullet
m1 mass = 20 g = 0.02 kg
u1 = 0
v1 = + 150 m/s
Pistol
m2 = 2kg
u2 = 0
v2 = ?
Total momentum of the pistol and bullet before firing, when the gun is at rest
= m1u1 + m2u2
= (0.02 x 0) + (2 x 0)
= 0 kg m/s
Total momentum of the pistol and bullet after it is fired
= m1v1 x m2v2
= (0.02 kg x 150) + (2 kg x v)
= 3 + 2v
∴ Total momentum after firing = Total momentum before firing
3 + 2v = 0
∴ v = \(\frac{-3}{2}\) = -1.5 m/s