Speed of Pendulum: Solving for Bob at Bottom of String

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SUMMARY

The discussion focuses on calculating the speed of a pendulum bob at the bottom of a 2.0-meter long string released from a 25-degree angle. The key equations involved are the potential energy (PE = mgy) and kinetic energy (KE = 1/2mv^2) formulas. The height of the bob at the 25-degree angle is determined using trigonometric functions, specifically h = 2.0 - (2.0)cos(25). This height is crucial for converting potential energy to kinetic energy to find the speed at the lowest point of the swing.

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Homework Statement


A 2.0 M long pendulum released from rest with the support string at an angle of 25 degrees with the vertical. What is the speed of the bob at the bottom of the string?

Homework Equations


PE = mgy
KE = 1/2mv^2
Trig functions

The Attempt at a Solution



I just need help getting the problem started, in the potential energy formula, we have two unknowns(unless the 2.0 m has to do with the location of the bob, but i am not certain).

Thanks in advance :]
 
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Yes, the 2.0m has something to do with the location of the bob. Use the bottom of the pendulum's course (2.0 m) as the reference point (at this point the PE is 0 and the KE is at a maximum).

Ill give you a shove in the right direction. Let's say the height of the bob at it's location at 25 degrees to the vertical is 2.0 - (2.0)cos25.

Hope this helps.
 

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