Quick Thermal Dynamics Question

AI Thread Summary
The discussion revolves around a thermal dynamics question related to the length of a brass rod used as a pendulum in a grandfather clock. The original poster struggled with the correct formula, initially applying the linear expansion equation without considering the pendulum's period. The correct approach involves using the formula for the period of a simple pendulum, T = 2π√(L/g). Ultimately, the poster realized their mistake and acknowledged the correct method. The conversation highlights the importance of understanding both thermal expansion and pendulum mechanics in solving the problem.
benji
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So we had a "quick quiz" a while back and I forgot about it and completely bombed it. I understand everything I did wrong now except for one part... Here's the question:

A brass rod (thermal expansion coefficient of 18.5*10^-6 (deg. celsius)) is used as a pendulum in a grandfather clock. The clock keeps perfect time at 20 (deg. celsius).

What is the length of the rod? (hint: how much time does it take the pendulum of a grandfather clock to go tick-tock?)

Originally I just used:

(change in length)=(coefficient of liner expansion)(original length)(change in temperature)

* sorry I don't know all the fancy code you guys use to make everything look all pretty ;) *

...that wasn't taking into account the time it takes to go "tick-tock" and I'm pretty sure it was the wrong equation.


So how should I go about this and why?

Thanks!
 
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period of a pendulum

You need to use the formula for the period of a simple pendulum:
T = 2\pi \sqrt{L/g}
 
Okay, nevermind I figured it out. You were right ;). Thanks.
 
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