# Answer to Question #3845 in Mechanics | Relativity for mia

Question #3845

A 4.00 kg model rocket is launched, shooting 50.0 g of burned fuel from its exhaust at an

average velocity of 625 m/s. What is the velocity of the rocket after the fuel has burned?

(Ignore effects of gravity and air resistance.)

average velocity of 625 m/s. What is the velocity of the rocket after the fuel has burned?

(Ignore effects of gravity and air resistance.)

Expert's answer

Let m

V

V

According to the law of conservation of linear momentum:

0 = m

V

V

So, the velocity of the rocket is 7.8 m/s.

_{1}be the mass of the rocket, m_{2}- the mass of burned fuel.V

_{1}- velocity of the rocket after the fuel has burned,V

_{2}- average velocity of burned fuel.According to the law of conservation of linear momentum:

0 = m

_{1}V_{1 }- m_{2}V_{2}V

_{1 }= V_{2}*m_{2 }/ m_{1}V

_{1 }= 625*0.05/4 = 7.8125 m/sSo, the velocity of the rocket is 7.8 m/s.

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