Completely stuck with mechanics question- please help!?

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hannah d

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student A has a mass of 75 kg and student B has a mass of 57 kg. They sit in identical office chairs facing each other. Student A places his bare feet on the knees of student B, as shown. Student A then suddenly pushes outward with his feet causing both chairs to move. If student A moves away with velocity, v, then student B moves away with what velocity? (Do not evaluate any fractions but write them explicitly).
 
Well you just use conservation of momentum. They both started with 0 momentum, which gives us nothing to work with, so look at what happens after they push apart. Then, 75v+57w=0 or 75v=-57w (w is the velocity of student B). w=-75v/57 the negative refers to the direction of student B. Away from the center is not specific, but opposite of the direction of v is specific.
 
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