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A $2.0 \space kg$ block, initially moving at $10.0 \space m/s$, slides $50.0 \space m$ across a sheet of ice before coming to rest. What is the magnitude of the average frictional force on the block?

I know the answer is 2.0 N.

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    This question seems ambiguous to me. Do you mean the average over time, or the average over distance? If you mean the former, then I don't think there's enough information to solve the problem. You might get a better insight if you ask on http://physics.stacke$x$change.com.2012-09-30

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$F_f^2 = F_0^2 + 2a(\Delta x)$

$F_f = 0 m/s$

$F_0 = 10 m/s$

$\Delta x = 50 m$

$a = -1 m/s$

$F = ma = 2 * -1 = -2N$ (negative because opposite to direction of motion)

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    You should be able to convert $F = -2$ to $|F| = 2$. ($|F|$ is what the problem asks for.)2013-06-30