(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A student ties a 400g rock to a 1.0m long string and swings it around her head in a horizontal circle. What angular speed does the string tilt down at a 10° angle?

m = 400g = .4kg

r = 1m

2. Relevant equations

[tex]F = \frac {mv^2}{r}[/tex]

[tex]\omega = \frac {|v|sin \theta}{|r|}[/tex]

[PLAIN]http://img31.imageshack.us/img31/7350/circ1.png [Broken]

[PLAIN]http://img513.imageshack.us/img513/513/circ2.png [Broken]

3. The attempt at a solution

First I solved for the tensions:

[tex]T_y = 9.8 * .4 = 3.92N[/tex]

[tex]tan 10 = \frac {3.92}{T_x}[/tex]

[tex]T_x = 22.23N[/tex]

Then for velocity:

[tex]22.23 = .4 * \frac {v^2}{1}[/tex]

[tex]v = 7.45 m/s[/tex]

Then for angular speed:

[tex]\omega = \frac {7.45 sin 10} {1}[/tex]

[tex]\omega = 1.29°/sec[/tex]

I wasn't sure if I set this up correctly or used the right formulas. I also wasn't sure if my answer was in the correct units. I also wanted to know if the picture for this motion is like the 1st picture or the 2nd picture? I used the first picture to solve this problem.

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# Homework Help: Angular speed; horizontal circle

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