How Do You Calculate Initial Speed in an Inelastic Collision?

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SUMMARY

The discussion focuses on calculating the initial speed of Kevin, who weighs 87 kg, before he collides with his 22-kg brother during an inelastic collision. The correct formula for this scenario is Mv = (M + m)v_f, where M is Kevin's mass, m is his brother's mass, and v_f is the final velocity after the collision. The final speed calculated should be greater than 3 m/s, as the momentum is conserved and Kevin gains speed by picking up his brother. The correct initial speed is determined to be 3.0 m/s, confirming the need for accurate application of the inelastic collision equations.

PREREQUISITES
  • Understanding of inelastic collisions and momentum conservation
  • Familiarity with basic algebra for rearranging equations
  • Knowledge of mass and velocity units (kg and m/s)
  • Experience with physics problem-solving techniques
NEXT STEPS
  • Study the principles of momentum conservation in inelastic collisions
  • Learn how to apply the equation Mv = (M + m)v_f in various scenarios
  • Explore examples of inelastic collisions in real-world applications
  • Practice solving similar physics problems involving mass and velocity
USEFUL FOR

This discussion is beneficial for physics students, educators, and anyone interested in understanding the dynamics of inelastic collisions and momentum conservation principles.

pstfleur
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1. Kevin has a mass of 87kg and is skating with in-line skates. He sees his 22-kg younger brother up ahead standing on the sidewalk, with his back turned. Coming up from behind, he grabs his brother and rolls off at a speed of 3.4 m/s. Ignoring friction, find Kevin's speed just before he grabbed his brother.



2. VF(ma+mb)=MTVF



3. From the problem I know it is an inelastic collision..
I did v= 87*v+22*2.4/109
v=2.4 which is wrong. the answer is suppose to be 3.0

Please help.. I really don't think I've grasped the idea of collisions
 
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You have the correct equation in the second part. I will rewrite it for you.

[tex]Mv=(M+m)v_f[/tex]

All you have to do is rearrange and find v.

The answer should also be greater than 3. How can he gain speed if he picks up his little brother as well.
 

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