Pendulum - Kinetic Energy at Lowest Point?

AI Thread Summary
The discussion centers on calculating the kinetic energy of a pendulum bob at its lowest point, given a length of 1.0 m and a mass of 0.2 kg, released from a 30-degree angle. The key point is the application of conservation of energy, where maximum potential energy converts to maximum kinetic energy at the lowest point. The potential energy is calculated using the formula U = mgy, with the height derived from the pendulum's release angle. The final calculation yields a kinetic energy of 0.26 J, confirming the professor's answer. This demonstrates the principles of energy conservation in pendulum motion.
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[SOLVED] Pendulum - Kinetic Energy at Lowest Point?

1. The Problem Statement:

A pendulum of length L= 1.0 m with an attached bob of mass m= 0.2 kg is released from a point where the cord makes an angle of 30 degrees with the vertical. The kinetic energy of the bob at its lowest point is...?
a. 2.0 J,
b. 1.7 J,
3. 1.1 J,
4. 1.0 J,
5. 0.26 J

Homework Equations


I believe Relevant equations include:
(1/2)mv^2 -- kinetic energy
(mgy) -- potential energy

The Attempt at a Solution


I know that at the lowest point in the pendulum, it is the highest speed. There is no potential energy. But, how do I get the value for velocity?
 
Last edited:
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Well from conservation of energy, the maximum potential energy is equal to the maximum kinetic energy. Can you calculate the maximum potential energy?
 
Ok so Maximum potential energy would be where it is released...
Thus,
U= gmy
(9.8)(0.2)(y)
and (y) is the height it is released so when I solve for that
and I get (1-cos(30)
U=gmy
(0.2)(9.8)(1-cos(30))
=0.26

and I just realized that my professor said the answer was E.
Thank you!
 
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