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## Homework Statement

Newton's cradle. Each ball is

**50 g**. First ball is raised to

**3.0 cm**, and the final ball reaches

**2.6 cm**after the collision.

1) Use the law of conservation of energy to calculate its velocity before impact.

2) Use the law of conservation of momentum to determine the velocity of the ball on the other side after the collision.

## Homework Equations

Ek + Ep = Ek + Ep (+ W; is W relevant here?)

m

_{1}v

_{2}+ m

_{2}v

_{2}= m

_{1}v

_{2}' + m

_{2}v

_{2}'

## The Attempt at a Solution

1) Ek + Ep = Ek + Ep

1/2mv

_{i}

^{2}+ mgh

_{1}= 1/2mv

_{f}

^{2}+ mgh

_{2}

0 + (0.050kg)(9.80m/s

^{2})(0.030m) = 1/2(0.050kg)v

_{f}

^{2}+ 0

v

_{f}= 0.7668 m/s

2) p = p'

m

_{1}v

_{2}+ m

_{2}v

_{2}= m

_{1}v

_{2}' + m

_{2}v

_{2}'

(0.050kg)(0.7668m/s) + 0 = 0 + (0.050kg)v

_{2}'

v

_{2}' = 0.7668 m/s

Is the height of the final ball involved in any of the calculations? I feel like it should be, but I can't figure it out.