Maximum kinetic energy of a pendulum

AI Thread Summary
The discussion centers on calculating the maximum kinetic energy of a pendulum with a mass of 3.2 kg and a length of 1.5 meters, swinging through an arc of 17 degrees. The user calculated the potential energy (PE) to be approximately 13.767 Joules but received feedback from an online checker indicating the correct value is 2.1 Joules. The discrepancy arises from an incorrect calculation of the height of the pendulum bob at 17 degrees. The user seeks clarification on whether their method is flawed or if the online tool is inaccurate. Accurate height determination is crucial for correctly calculating potential energy and, subsequently, maximum kinetic energy.
jforce93
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Homework Statement


Okay, so I'm using the online Giancoli physics thing for AP Physics C summer work (see: "([PLAIN]http://wps.prenhall.com/esm_giancoli_physicsppa_6"[/URL]. I think my way of doing it is correct, but the online checker says I'm wrong.
The question: "A pendulum has a mass of 3.2 kg, a length of 1.5 meters, and swings through a (half)arc of 17 degrees. To the nearest tenth of a Joule, what is its maximum kinetic energy of the pendulum?"

Homework Equations


PE = mgh
KE = 1/2mv^2


The Attempt at a Solution


Find the PE of the pendulum. The height of it at 17 degrees: .43856 meters (about).
PE = 3.2*9.81*.43856 = 13.767 Joules. But the online checker says 2.1 Joules.

What am I doing wrong? Or, am I doing it right, the online thing is just wrong?

Thanks,

Jordan
 

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Your height for the pendulum bob is not correct.
 

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