Two cars intially at rest are free to move in the `x` direction. Car `A` has mass 4 kg and car `B` has mass 2kg. They are tied together, compressing a spring in between them. When the string holding them together is burned, car `A` moves off with a speed of `2//s` (a) with what speed does car `B` leave. (b) how much energy was stored in the spring before the string was burned.

Two cars intially at rest are free to move in the `x` direction. Car `

1.	Two cars intially at rest are free to move in the `x` direction. Car `A` has mass 4 kg and car `B` has mass 2kg. They are tied together, compressing a spring in between them. When the string holding them together is burned, car `A` moves off with a speed of `2//s` (a) with what speed does car `B` leave. (b) how much energy was stored in the spring before the string was burned.
Answer» Correct Answer - 4m/s, 24J (a) `m_(A)v_(A)+m_(B)+v_(B)=0` [Initially both of them were at rest] `rArrv_(B)=-(m_(A)v_(A))/(m_(B))=-((4)(2))/((2))=-4m//s` (b) `E=(1)/(2)m_(A)v_(B)^(2)+(1)/(2)m_(B)v_(B)^(2)` `rArrE=(1)/(2)(4)(2)^(2)+(1)/(2)(2)(-4)^(2)=24J`

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