Momentum Changes in a variable mass system.

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SUMMARY

The discussion focuses on momentum changes in variable mass systems, specifically in the context of a rocket's mass decreasing as fuel is expelled. The relevant equation presented is m(t)a = Rv, where R represents the rate of mass loss and v denotes the velocity of the ejected gas. Participants suggest using examples from Michael Richmond's website, which provides data on rockets and their fuel usage. Additionally, simpler examples involving cars are recommended to avoid complications from gravity and air resistance, making the topic more accessible for high school students.

PREREQUISITES
  • Understanding of the equation m(t)a = Rv in variable mass systems
  • Basic knowledge of momentum and acceleration concepts
  • Familiarity with calculus principles, particularly in relation to rates of change
  • Awareness of real-world applications of physics in rocket propulsion
NEXT STEPS
  • Research the application of the Tsiolkovsky rocket equation in variable mass systems
  • Explore examples of momentum changes in car dynamics without external forces
  • Study the effects of fuel consumption on rocket performance using real data
  • Learn about the principles of conservation of momentum in variable mass scenarios
USEFUL FOR

Students preparing for AP Calculus, physics educators seeking simplified examples, and anyone interested in the dynamics of variable mass systems in physics.

Faustian
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Pleeeease help me. I have to do a twenty minute presentation on momentum changes in variable mass systems. I have everything done but examples. The equation I have is m(t)a=Rv where R is the rate the mass of the rocket is decreasing and v is the velocity of the gas ejected with respect to the rocket. Does anyone have any examples from the internet I can use? At least any realistic variables? I have absolutely NO idea what realistic numbers would be for this situation. Actually, to be honest, I'm not really sure how to use the equation. What would I have to have to solve for a sample? The velocity of the particles ejected, the time and rate of change of the mass? Then I would just use the rate of change and the time to find m(t) and I would solve for a? :frown: This is actually for AP Calculus, but I'm pretty sure this concept is a bit advanced for the high school level (My physics teacher couldn't even help me, which is kind of sad). Please, any help will really be appreciated.
 
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Umm… ok. Well, that certainly sounds like an interesting presentation but a lot of work. I hope you're enjoying it.
There is a site by Michael Richmond, Dept. of Physics Rochester Institute of Technology, which should be helpful.
http://spiff.rit.edu/classes/phys311_t/workshops/w10a/rockets/rockets.html
It lists two rockets and the fuel used in there deployment. You might have already considered this, but using cars as examples might be simpler, as you don’t have to consider changes in gravity and air density.
 
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Thank you. That looks like it'll help. The thing is, most of the people in my calculus class haven't even taken a basic physics class. Because of this, I can make my problems as simple as possible. The samples I use won't even have ANY gravity or air resistance.
 

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