Question 1040014
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1. A 25 N object requires a 5.0 N to start moving over a horizontal surface. What is the coefficient of static friction?


<pre>
{{{k[friction]}}} = {{{F[shift]/F[normal]}}}

Coefficient of friction is the ratio of the magnitude (modulus) of the shifting force {{{F[shift]}}} applied to the body 
and directed along the surface to the magnitude (modulus) of the normal force {{{F[n]}}} directed normal to the surface (see <A HREF=https://en.wikipedia.org/wiki/Friction>this</A> Wikipedia article).


I  our case, {{{k[friction]}}} = {{{5/25}}} = 0.2.
</pre>

2. A 12 N cart is moving on a horizontal surface with a coefficient of kinetic friction of 0.20. What force of friction 
must be overcome to keep the object moving at a constant velocity?


<pre>
{{{F[friction]}}} = {{{k[friction]*F[n]}}} = 0.2*12 = 2.4 N.
</pre>

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