Solving a collision question, is there enough information?

AI Thread Summary
The discussion centers on a collision problem involving a 0.6 kg puck, where the user has derived three equations but faces four unknowns: mq, up, vp, and vq. Participants agree that there is insufficient information to solve the problem, noting the absence of the second mass is particularly suspicious. It is suggested that for the provided answers to be accurate, the mass of the other object (Q) must be approximately 0.7 kg. The consensus is that without this information, the problem cannot be resolved. The discussion concludes with an acknowledgment of the need for complete data to solve the equations effectively.
pkc111
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Homework Statement
See Q7 below about 0.6 kg puck.
Relevant Equations
Law of conservation of momentum and law of conservation of kinetic energy for elastic collisions.
See working attached.

My problem is that I have come up with 3 equations but 4 unknowns (mq, up, vp, vq). Is this problem solvable?

The answers say:
a) 0.5 m/s b) 0.65 m/s and c) 0.34 m/s

Many thanks
 

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pkc111 said:
Homework Statement:: See Q7 below about 0.6 kg puck.
Relevant Equations:: Law of conservation of momentum and law of conservation of kinetic energy for elastic collisions.

See working attached.

My problem is that I have come up with 3 equations but 4 unknowns (mq, up, vp, vq). Is this problem solvable?

The answers say:
a) 0.5 m/s b) 0.65 m/s and c) 0.34 m/s

Many thanks
You are right, there's not enough information. It is suspicious that you are only given one mass and not even asked for the mass of the other. This suggests to me you were supposed to be told both masses.

Edit: to get the given answers, Q has to have mass almost exactly 0.7kg. Case closed.
 
Thanks haruspex!
 
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