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## Homework Statement

A 0.5-kg rubber ball is dropped from rest a height of 19.6 m above the surface of the Earth. It strikes the sidewalk below

and rebounds up to a maximum height of 4.9 m. What is the magnitude of the impulse due to the collision with the sidewalk?

## Homework Equations

J=[tex]\Delta[/tex]P

## The Attempt at a Solution

mgh=.5mv

^{2}

v=[tex]\sqrt{}2gh[/tex]

Just before collision:

v=[tex]\sqrt{}2*9.8*19.6[/tex]

v=19.6 m/s

Just after collision:

v=[tex]\sqrt{}2*9.8*4.9[/tex]

v=9.8 m/s

J=m(v

_{after}-v

_{before})=.5(9.8-19.6)=4.9 kg m/s

The answer is 14.7 N.s, so I'm not sure what I'm missing.