Pendumlum and Tension in String Question

[PeterPesto]

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Hi guys,

So the centripetal force in a pendulum is given by the tension in the string minus the component of gravity which acts opposite to this force.

So: Force Centripetal = Ft - mg cos (theta)

So if the centripetal force increases doesn't that increase the velocity of the mass? Force Centripetal = mv^2/r

However, I can't reconcile this with the equation for frequency, where only the string length affects frequency. Does the string length somehow affect the tension force in the string? If the velocity is increasing, shouldn't the frequency be decreasing?

 

[PeterPesto]

Oh wait, I just realized that velocity isn't constant 🙂

 

[ilovemcat]

Oh wait, I just realized that velocity isn't constant 🙂

Yeah, haha. I was like what... But good job 🙂

 

[phltz]

It's also worth noting that, at the level of physics the MCAT covers, pendulums are typically only considered when you can use the small angle approximation. With the small angle approximation, sin(theta) = theta, and cos(theta)=1. This simplifies your equation considerably.