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M2 help

Need help with 4i.

Don't really understand it.

I did :
Initial Ke + Inital GPE = Final KE + Finial GPE + wd by friction
160 + 0 = 1000+ 6703 + 1750
Is the work done just supposed to be on the left of the equation as both have to be equal?
Also is it always (+) wd by friction?

https://9565af48d144678aee5dbc2a15d45a3e01a9f8e9.googledrive.com/host/0B1ZiqBksUHNYbDZOTnhJd2J4ZkU/January%202007%20QP%20-%20M2%20OCR.pdf

Reply 1

ghostwalker

Original post by Super199

Your equation doesn't take into account the pulling force. You're not actually looking for an equation as such, rather a formula for the work done by the pulling force.

If we start with a more general formula.

"Work done by pulling force" = "gain in energies of object" + "work done against friction"

= "final KE - initial KE" + "final GPE - initial GPE" + "work done against friction"

And take it from there.