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## Homework Statement

A small box is resting on a larger box, which in turn sits on a table. When a horizontal force is applied to the larger box, both boxes accelerate together. The small box does not slip on the larger box.

a)Draw a free body diagram of the small box as it accelerates.

b)What force causes the small box to accelerate horizontally?

c) If the acceleration of the pair of boxes has a magnitude of 2.5 m/s^2, determine the smallest coefficient of friction between the boxes that will prevent slippage.

## Homework Equations

F=ma

F=mg

F(normal)=-mg

F(staticfriction)=(coefficientofstatic)(Fnormal)

F(staticfriction)=(coefficientofstatic)(-mg)

## The Attempt at a Solution

a) http://img233.imageshack.us/img233/109/fstaticti4.jpg [Broken]

b) The force applied on the large box

c)

Find when Fs is equal to Fa

So let Fs=Fa

Fs=(coefficientofstatic)(-mg)

Fa=ma

ma=(coefficientofstatic)(-mg)

a=(coefficientofstatic)(-g)

2.5m/s^2=(coefficientofstatic)(9.8m/s^2)

(coefficientofstatic)=2.5/9.8

(coefficientofstatic)=0.26

Therefore the coefficient of static friction must be 0.26

My friend and I got completely different final answers so I'm wondering if I'm wrong or right. Please help!

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