Find Initial Speed of Porsche Using Inelastic Collision

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SUMMARY

The discussion focuses on calculating the initial speed of a Porsche using principles of inelastic collision and momentum conservation. Participants emphasize the need to separate the momentum equations into two dimensions: North/South and East/West. The key equation used is momentum before = momentum after, represented as mv + mv = (m1+m2)v. Additionally, the solution involves applying the accelerated motion formula to find the speed post-collision using friction and distance data.

PREREQUISITES
  • Understanding of inelastic collisions and momentum conservation principles
  • Familiarity with 2D motion analysis
  • Knowledge of accelerated motion equations, specifically Vf = Vi + at
  • Ability to derive motion equations without time information
NEXT STEPS
  • Study the derivation of the accelerated motion formula without time
  • Learn about 2D momentum conservation in inelastic collisions
  • Explore the relationship between friction, distance, and speed in collision scenarios
  • Review graphical methods for analyzing velocity versus time relationships
USEFUL FOR

This discussion is beneficial for physics students, educators, and anyone interested in understanding the mechanics of collisions and motion analysis in two dimensions.

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Homework Statement


blah blah blah

Homework Equations


momentum = momentum'
mv + mv = (m1+m2)v
(Uk)N = friction force


The Attempt at a Solution



It's hard to find how to start with randomly given values.
Thank you so much for your help! :D
 
Last edited:
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It is a 2D problem so you must write two headings for North/South and East/West. Then write that "momentum before = momentum after". Follow that up with an "mv" for each moving object in each part. Then put in your numbers. If you are still having trouble, show us your work and someone will be pleased to pitch in and help!
 
No, I don't think any of it makes sense. Even the
1380kg v + 2304kg v = 3684kg v
can't be right because before the collision you don't have two vehicles moving in either the north/south or east/west direction. Got to write the two headings and two separate equations!

You do have to find the speed of the pair of them after the collision from the friction and distance information given. That is an ordinary 1D accelerated motion problem, a little complicated because there is no time info. Do you have the accelerated motion formula with v's, d and a but no t? That is perfect for the job. If you don't have it you could derive it by solving Vf = Vi + at for t and subbing into
d = Vi*t+.5*a*t^2. Or you could sketch the v vs t graph and use the fact that the area under the graph is the distance.
 

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