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## Homework Statement

## Homework Equations

ΔE

_{system}+ ΔE

_{surroundings}=0

## The Attempt at a Solution

I have solved 11a and got 5m/s.

I can do 11b just by just jumping to E

_{k}= Fs (from the work kinetic energy theorem), but I would like to do it formally from first principles using the Law of Conservation of Energy.

I would then like to make use of

ΔE

_{system}+ ΔE

_{surroundings}=0

and then make use of ΔE

_{system}= ΔU + ΔE

_{k}+ ΔE

_{p}

and then make use of ΔU = W + Q

and then introduce W = Fs

then solve for F.

However I am not sure where to put the system boundary so this is solvable. Then the question of the pluses and minuses.

Many thanks

Many thanks

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