High School

An astronaut at rest in space with a mass of 84 kg fires a thruster that expels 35 g of hot gas at 875 m/s. What is the velocity of the astronaut after firing the thruster?

Answer :

Answer:

about 0.365 m/s

Explanation:

You want to know the velocity of an astronaut who starts from rest and fires a thruster that expels 35 g of gas at 875 m/s.

Momentum

The total momentum of the system is the same before and after the thruster is fired: 0.

If v is the velocity of the astronaut, it must satisfy the equation ...

(84)v +(0.035)(875) = 0

v = -(0.035)(875)/(84) ≈ -0.3646

The velocity of the astronaut is about 0.365 m/s in the direction opposite of the expelled gas.

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Additional comment

We have used (kg·m/s) as the units of momentum. 35 g = 0.035 kg. We have also assumed that the mass of the system before firing is a total of 84.035 kg