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Ch 08: Momentum, Impulse, and Collisions
Young & Freedman Calc - University Physics 14th Edition
Young & Freedman Calc14th EditionUniversity PhysicsISBN: 9780321973610Not the one you use?Change textbook
Chapter 8, Problem 62a

A small rocket burns 0.0500 kg of fuel per second, ejecting it as a gas with a velocity relative to the rocket of magnitude 1600 m/s. What is the thrust of the rocket?

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1
Understand the concept of thrust: Thrust is the force exerted by the rocket due to the ejection of fuel. It is calculated using the formula: F=dmv, where dm is the rate of change of mass (mass of fuel burned per second) and v is the velocity of the ejected gas relative to the rocket.
Identify the given values: The problem states that the mass of fuel burned per second is 0.0500 kg/s, and the velocity of the ejected gas relative to the rocket is 1600 m/s.
Substitute the given values into the thrust formula: F=dmv=0.05001600.
Simplify the expression to calculate the thrust: Perform the multiplication of the mass flow rate and the velocity of the ejected gas to find the thrust.
Interpret the result: The calculated thrust represents the force exerted by the rocket due to the ejection of fuel, measured in newtons (N).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Thrust

Thrust is the force exerted by a rocket or engine to propel it forward. It is generated by the expulsion of mass (in this case, fuel) at high velocity. According to Newton's third law, for every action, there is an equal and opposite reaction, meaning that the force of the expelled gas creates an upward thrust that propels the rocket.
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Conservation of Momentum

The conservation of momentum principle states that the total momentum of a closed system remains constant if no external forces act on it. In the context of rockets, as fuel is expelled, the momentum gained by the rocket in the opposite direction is equal to the momentum lost by the expelled fuel, allowing us to calculate thrust based on the mass flow rate and velocity of the exhaust.
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Mass Flow Rate

Mass flow rate is the amount of mass that passes through a given surface per unit time, typically expressed in kilograms per second (kg/s). In rocket propulsion, it is crucial for calculating thrust, as it directly relates to how much fuel is consumed and how quickly it is expelled, influencing the overall performance and efficiency of the rocket.
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