The body m1 = 2 kg lies on a horizontal plane, it was hit by a bullet m2 = 10 g, the speed of the body is 2 m / s.

The body m1 = 2 kg lies on a horizontal plane, it was hit by a bullet m2 = 10 g, the speed of the body is 2 m / s. Find the speed of the bullet.

To find the speed of a given body after being hit by a bullet, we use the equality (the law of conservation of momentum, the impact of a bullet on a given body is considered inelastic): mp * Vp = (mt + mp) * Vpt, whence we express: mp.
Values of variables: mt – body weight (mt = 2 kg); mp – bullet mass (mp = 10 g = 0.01 kg); Vпт – the speed that a given body has acquired (Vпт = 2 m / s).
Calculation: Vpt = (2 + 0.01) * 2 / 0.01 = 402 m / s.
Answer: The bullet before hitting the target body had to have a speed of 402 m / s.