Solving a collision question, is there enough information?

[pkc111]

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

 

[haruspex]

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.

 

[pkc111]

Thanks haruspex!