The 30 lb box A is released from rest and slides down along the smooth ramp and onto the surface. Determine the distance s from the end of the surface to where the box stops. The coefficient of kinetic friction between the cart and the box is [itex]\mu_k\,=\,0.6[/itex].(adsbygoogle = window.adsbygoogle || []).push({});

http://img224.imageshack.us/img224/8509/problem14343jq.jpg [Broken]

Here is what I have so far:

[tex]-W\,\Delta\,y\,=\,(-30\,lb)\,(-4\,ft)\,=\,120\,ft\,lb[/tex]

[tex]\sum\,F_y\,=\,N\,-\,W\,=\,0\,\Rightarrow\,N\,=\,W\,=\,30\,lb[/tex]

[tex]\sum\,F_x\,=\,-f_k\,=\,m\,a_x\,\Rightarrow\,-\mu_k\,N\,=\,m\,a_x[/tex]

[tex](-0.6)\,(30\,lb)\,=\,(0.932)\,a_x[/tex]

[tex]a_x\,=\,\frac{-18.6}{0.932}\,=\,-19.3\,\frac{ft}{s^2}[/tex]

Now what?

I know I need to find [itex]v_f[/itex] and the bottom of the hill and I am probably supposed to use a work-energy equation?

[tex]\sum\,T_1\,+\,\sum\,U_{1\,-\,2}\,=\,\sum\,T_2[/tex]

Please help, thanks.

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# Homework Help: Block slides 4ft down a smooth plane & then slides on a rough surface (0.6) - s = ?

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