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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.
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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: ->->->->->->->->->->->-> n:
m1v1 + m2v2 = m1v1’ + m2v2’
(60g * 80cm/sec) + (20g * 0m/sec) = (60g * 50cm/sec) + (20g * 70cm/sec)
4800g*cm/sec = 3000g*cm/sec + 1400g*cm/sec
After collision, the momentum has decreased by 400g*cm/sec. I believe this loss would be to heat being release on impact.
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A loss in total KE would be due largely to thermal energy created by the impact.
However that would not entail a momentum change. The only way the momentum of the system would change would be if there are external forces acting on the system.
Of course these could be experimental observations, subject to experimental errors or uncertainties.
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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: ->->->->->->->->->->->-> n:
4800g*cm/sec = 3000g*cm/sec + 20g * v_marble
1800g*cm/sec = 20g * v_marble
v_marble = 90cm/sec
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15m
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&#Your work looks good. See my notes. Let me know if you have any questions. &#