Phy 121
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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: before collision p1 = m1v1 = .060kg*.8m/s = .048kgm/s p2 = m2v2 = .020kg*0 = 0 since it was stationary, after collision p1 = m1v1 = .060kg*.5m/s = .030kgm/s p2 = m2v2 = .020kg*.7m/s = .014kgm/s , so momentum before collision = .048kgm/s and momentum after collision = .044kgm/s
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: 90cm/s , so p1 = m1v1 = .060kg*.8m/s = .048kgm/s p2 is 0 since the marble is stationary, then after collision p1 = m1v1 = .060kg*.5m/s = .03kgm/s, p2 = m2v2 = .020kg*.9m/s = .018kgm/s and .03kgm/s + .018kgm/s = .048kgm/s which is equal to the momentum of the system before the collision
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20min
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