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.)

Expert's answer

Let m_{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/s

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

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.

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