Speed of Pendulum: Solving for Bob at Bottom of String

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    Pendulum Speed
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To find the speed of the pendulum bob at the bottom of the string, start by determining the height of the bob when released from a 25-degree angle. The potential energy (PE) at this height can be calculated using the formula PE = mgy, where y is the height difference from the lowest point. At the bottom, the potential energy is zero, and all energy is converted to kinetic energy (KE = 1/2mv^2). The height can be found using the equation y = 2.0 - (2.0)cos(25), which will allow for the calculation of the bob's speed at the lowest point. This approach effectively utilizes energy conservation principles in pendulum motion.
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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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