The cable at C is being pulled down at a velocity of [tex]4 \frac{ft}{s}[/tex]. The cable at C is also decelerating at a rate of [tex]2 \frac{ft}{s^2}[/tex]. At what velocity and acceleration is the block at A moving?(adsbygoogle = window.adsbygoogle || []).push({});

http://img222.imageshack.us/img222/729/engr204problem121795wl.jpg [Broken]

I have the following equations for the problem worked out:

[tex]\ell\,=\,2\,S_A\,+\,\left(h\,-\,S_B\right)[/tex]

[tex]\frac{d}{dt}\,\left[\ell\,=\,2\,S_A\,+\,\left(h\,-\,S_B\right)\right][/tex]

[tex]0\,=\,2\,V_A\,-\,V_B[/tex]

[tex]V_A\,=\,-\frac{V_C}{2}[/tex]

[tex]V_A\,=\,-\frac{-4}{2}\,=\,2\,\frac{ft}{s}[/tex]

This answer is NOT correct, it is off by a factor of two. Can anyone tell why?

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# Homework Help: Pulley Problem for Engineering Dynamics Course

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