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## Homework Statement

A ball of mass 4.5 kg is moving 16 m/s east when it collides with a stationary 6.2kg ball, which moves at a velocity 10 m/s after the collision. Was this an elastic or inelastic collision? Explain your choice.

Va = 16 m/s

Ma = 4.5 kg

Mb = 6.2 kg

Vb' = 10 m/s

## Homework Equations

MaVa + MbVb = MaVa' + MbVb'

## The Attempt at a Solution

Let east be positive.

MaVa + MbVb = MaVa' + MbVb'

4.5(16) + 0 = 4.5Va' + 6.2(10)

72 = 4.5Va' + 62

10 = 4.5Va'

2.22 = Va'

From doing the above I would say it is an elastic collision. However, from what the answers the teacher gave us it is supposed to be an inelastic collision, can anyone tell me how this is so?