Two skater's momentum after collision

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    Collision Momentum
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Homework Help Overview

The problem involves a collision between two skaters, Daisy and her friend, where momentum conservation is to be applied to determine their combined speed after the collision. The scenario includes specific masses and initial velocities, with multiple choice answers provided for the final speed.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the conservation of momentum and attempt to set up equations based on the given masses and velocities. Some express confusion regarding the correct application of the momentum formula, while others offer alternative formulations and solutions.

Discussion Status

There is an ongoing exploration of the correct approach to the problem, with some participants providing guidance on the conservation of momentum. However, there is no explicit consensus on the correct final speed, as different interpretations and calculations are being discussed.

Contextual Notes

Some participants note a lack of clarity regarding the initial conditions, specifically the velocity of the second skater, which may affect the setup of the problem. Additionally, there are references to multiple choice answers that may not align with the calculations being discussed.

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Homework Statement



Daisy (50-kg mass) skates on ice at 4.0 m/s to greet her friend (70-kg mass), who is standing still, with open arms. As they collide, while holding each other, with what speed do they both move off together?

A. Zero
B. 1.7 m/s
C. 2.5 m/s
D. 5.0 m/s

Homework Equations


mi(vf-v1)=m2(vf-v1)
?

The Attempt at a Solution



50kg(vf-4m/s)=70kg(vf-0m/s)

I find that if I try to solve for vf, the other vf cancels it out, so I know i am not doing something right. Can anyone help?
 
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i believe you have your formula wrong

p1=p2.
M1V1i+M2V2i=Vf(M1+M2)
 
Momentum must be conserved. For part a pi=pf, where pi=m1v1+m2v2. You know the collision is ineslatic so the 2 gals move off together so pf=vf(m1+m2) where vf is your unknown. Solve for vf. I get 1.66 m/s
 
that isn't even one of the options.
 
i am not given the velocity of the skater at anytime, i have no clue how to do this
 
oh hey, I am sorry, you are right, i was looking at the wrong problem when i wrote that. 1.67 is correct
 
Yes, but rounded up it is 1.7 m/s so b is the answer. Good luck!
 

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