- #1

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## Homework Statement

given:

m=1.0x10^4kg

a relative speed of 1200m/s

t=2.0

F=25kN

pi=?

pf=?

## Homework Equations

## The Attempt at a Solution

(-25*10^3)(2.0)=(1.0x10^4)(1200)+(1.0*10^4)(mvi)

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- Thread starter jamiescience
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- #1

- 8

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given:

m=1.0x10^4kg

a relative speed of 1200m/s

t=2.0

F=25kN

pi=?

pf=?

(-25*10^3)(2.0)=(1.0x10^4)(1200)+(1.0*10^4)(mvi)

- #2

dynamicsolo

Homework Helper

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I take it that a 25,000 N force is being applied to the mass for 2 seconds. It's not clear how to proceed until we know what that velocity is for...

- #3

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- #4

dynamicsolo

Homework Helper

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What is the relationship between force and change of momentum? You can find the momentum change caused by the thruster, which will let you find the final momentum. (Your equation has the right ideas, but in the wrong sequence...)

- #5

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(-25*10^3)(120)= (1.0*10^4)(mvi)-(1.0x10^4)(1200)

- #6

dynamicsolo

Homework Helper

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(-25*10^3 N)(120 sec)= (1.0*10^4 kg)(

Your left-hand side is fine. The right-hand side is the change in momentum. You already have the mass in the first term there, so I have corrected the factor that should be just the final velocity.

Since you are just asked for the initial and final momenta, you really only need to calculate the products. You already have the one for the initial momentum, so you now just need to find the first product on the right-hand side, which is the final momentum.

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