cq_1_242

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PHY 121

Your 'cq_1_24.2' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.

** CQ_1_24.2_labelMessages **

A steel ball of mass 60 grams, moving at 80 cm / sec, collides with a stationary marble of mass 20 grams. As a result of the collision the steel ball slows to 50 cm / sec and the marble speeds up to 70 cm / sec.

Is the total momentum of the system after collision the same as the total momentum before?

answer/question/discussion: ->->->->->->->->->->->-> :

It is close.

Before: m * v = .06 kg * .8 m/s = .048 kg m/s for Object 1

m * v = .02 kg * 0 m/s = 0 kg m/s for Object 2

Total before: .048 km m/s

After: m * v = .06 kg * .5 m/s = .03 kg m/s

m * v = .02 kg * .7 m/s = .014 kg m/s

Total after: .044 kg m/s

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What would the marble velocity have to be in order to exactly conserve momentum, assuming the steel ball's velocities to be accurate?

answer/question/discussion: ->->->->->->->->->->->-> :

Total before - steel ball after = marble after

.048 kg m/s - .03 kg m/s = .018 kg m/s

.018 kg m/s / .02 kg = .9 m/s

It would need to be going .9 m/s instead of .7 m/s.

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&#Very good responses. Let me know if you have questions. &#