- #1

Pao44445

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## Homework Statement

a bullet 15 g travels 300 m/s then hit the plastic sheet that is thick 2 cm and pass through it. After the crash, the bullet travels 90 m/s ( continue to lose the velocity ) How much the average force acting on the bullet?

## Homework Equations

Momentum = Mass x Velocity

## The Attempt at a Solution

From the diagram, While the bullet is travelling, it has momentum (15x10

^{-3})(300) = 4.5 kg(m/s) and after the crash, it has momentum (15x10

^{-3})(90) = 1.35 kg(m/s)

4.5 - 1.35 = 3.15 kg(m/s)

the change in momentum is equal to Impulse

Impulse = 3.15 kg(m/s)

F(t) = 3.15 kg(m/s)

I found the time with S=ut+1/2at

^{2}

2x10

^{-2}= 300(t) + 1/2[(90-300)/t](t)

^{2}

t is about 1x10

^{-4}s

F(10

^{-4}) = 3.15 kg(m/s)

F = 3.15x10

^{4}N