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Two balls roll towards each other. The red ball has a mass kg 0.5 kg and a speed of 4 m/s just before impact. The green ball has a mass of 0.3 kg and a speed of 2m/s. after the head-on collision, the red ball continues forward with a speed of 2m/s. find the speed of the green ball after the collision. was the collision elastic? |
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Answer» Solution :First remember that MOMENTUM is a vector quantity, so the direction of the velocity is crucial. Since the balls roll TOWARD each other, one ball has a positive velocity while the other has a negative velocity. Let's call the red ball's velocity before the collision positive, then `v_(red)=+4m//s, and v_("green")=-2m//s.` using a PRIME (') to denote after the collision, CONSERVATION of linear momentum GIVES us the following: total `p_("before")=`total `p_("after")` `m_(red)v_(red)+m_("green")v_("green")=m_(red)v_(red)'+m_("green")v_("green")'` `(0.5)(+4)+(0.3)(-2)=(0.5)(+2)+(0.3)v_("green")'` `v_("green")'=+1.3m//s` |
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