(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A massless spring of spring constant 20 N/m is placed between two carts. Cart 1 has a mass M1 = 5 kg and Cart 2 has a mass M2 = 2 kg. The carts are pushed toward one another until the spring is compressed a distance 1.5 m. The carts are then released and the spring pushes them apart. After the carts are free of the spring, what are their speeds?

2. Relevant equations

I am using K_f + U_f = K-i + U_i

Why doesnt it work?

3. The attempt at a solution

OK heres what I know

U_i = 1/2k delta s^2

= 22.5J

K_i = 0 (because object initially not moving)

U_f = 0 (because carts now moving)

K_f = 1/2 mv^2

Energy is conserved, so 1/2mv^2 must = 22.5J.

Also, 22.5J is the kinetic energy of BOTH carts

So 22.5J = K (of cart 1) + K (of cart 2)

so that leaves me with 2 unknowns in each equation for each cart???

1/2mv^2 (cart 1) = (some amount of 22.5J)

1/2mv^2 (cart 2) = (some amount of 22.5J)

Please Help,

(Thanks)

(ALSO, I do understand that potential E is converting to kinetic E and the amount is conseved

and also that momentum is conserved)

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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# Homework Help: Energy conservation (2 carts and a spring)

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