How can I calculate kinetic friction?

1. Oct 23, 2016

Rick devena

1. The problem statement, all variables and given/known data

A child slides down a slide with a 28 degree incline , and at the bottom her speed is precisly half what it would have been if the slide had been frictionless. Calculate the coefficient of kinetic friction between the slide and the child.
2. Relevant equations

Newtons second law
3. The attempt at a solution

https://www.physicsforums.com/attac...6/?temp_hash=7d75ca4df687186214dd365d2dd18568

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2. Oct 24, 2016

Simon Bridge

I don't understand your writing ... I kinda see a diagram showing some forces, but I don't see a friction force on it, unless that's the "F" pointing down the slide.
There's something that looks like script-written "Als" ... maybe a scribbled $\mu_s$ or something ... cannot tell.
Please explain your reasoning.

3. Oct 24, 2016

haruspex

There are several things wrong with your equations.
If mg is the gravitational force and the slope is θ, what is the normal force, and what is the downslope component of gravity?

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