Momentum Relative to Surface / Plug-and-Chug

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SUMMARY

The discussion revolves around a physics problem involving momentum conservation in a system with a stationary rolling platform and a person walking on it. The platform has a mass of 76 kg, and the person, Stevie, has a mass of 43 kg. Using the conservation of momentum equation, the velocities of both the platform and Stevie relative to the floor were calculated, resulting in values of -0.43 m/s for the platform and 0.77 m/s for Stevie. The key takeaway is the importance of accounting for the combined mass of the system when applying momentum conservation principles.

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Homework Statement



Stevie stands on a rolling platform designed for moving heavy objects. The platform has mass of 76 kg and is on a flat floor, supported by rolling wheels that can be considered to be frictionless. Stevie's mass is 43 kg. The platform and Stevie are stationary when she begins walking at a constant velocity of +1.2 m/s relative to the platform. (a) What is the platform's velocity relative to the floor? (b) What is Stevie's velocity relative to the floor?

Homework Equations



(p)i = (p)f Conservation of Momentum


The Attempt at a Solution



Used Conservation of Momentum, but I am having trouble establishing a reference point.

43x1.2 + 76xV2f = 0 - That's for the the platform and Stevie.

.521x119 = 43xV1f + 76xV2f - That's for the entire system...I think.

As stated above, I think my problem is finding the reference point. I would normally spend more time with this one by myself, but I have a quiz on this fairly soon.


The answers:
(a) −0.43 m/s
(b) 0.77 m/s
 
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Your first equation would give you the correct answer if you considered that the platform has additional mass as a result of someone standing on it.
 
Of course it would.

You're the man BishopUser. Thanks dude.
 

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