- #1
crafty2288
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Homework Statement
A plank of length 6m is lying on a smooth horizontal surface and has a mass of 100kg. A 50kg girl walks from one end of the plank to the other. In this experiment, how far will the plank shift and what direction? Why?
Homework Equations
v_g will mean girl's velocity relative to ice.
v_p will mean plank's velocity relative to ice.
M(girl)V(girl)[initial] + M(plank)V(plank)[initial] = M(girl)V(girl)[final] + M(plank)V(plank)[final]
The Attempt at a Solution
I feel like I need the girl's velocity or I can't do this. I understand how to solve it, but can anyone help me to understand how I do it without knowing the girl's velocity?
Initial momentum = 0 (because she's at rest).
Final momentum = 0 (because it has to equal initial momentum)
M(girl)V(girl)[initial] + M(plank)V(plank)[initial] = M(girl)V(girl)[final] + M(plank)V(plank)[final]
0 + 0 = (50)*V(girl)f + (100)*V(plank)fOr am I making this harder than it needs to be?