Pendulum speed with only height from equilibrium

AI Thread Summary
To find the speed of a pendulum passing through the equilibrium position after being dropped from 0.50 meters, the conservation of energy principle is applied. The potential energy at the height of 0.05 meters is converted entirely into kinetic energy at the equilibrium point. The relevant equation, mgh = (1/2)mv², allows for mass to cancel out, simplifying the calculation to v = √(2gh). With g as 9.81 m/s² and h as 0.05 m, the speed can be calculated directly without needing the mass. The discussion concludes with the realization that the mass is irrelevant for determining the speed at equilibrium.
Serpentia
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Homework Statement


A pendulum is dropped from 0.50 metres above the equilibrium position. What is the speed of the pendulum as it passes through the equilibrium position? (The pendulum is in a isolated system.)

h1= 0.05m
h2= 0.00m
g= 9.81 m/s^2
Length of string (L)= 1.0m.

Homework Equations


Em=Ek+Ep
Em=[(1/2)mv^2]+[mgh]
v=√(2Ek/m)


The Attempt at a Solution



I'm not entirely sure what to try. I'm not given mass, or any value of any form of Energy, be it Kinetic or Gravitational Potential. I've tried to find the value of mass, but I don't have the energy or velocity factor to figure it out;

v=√(2Ek/m)
m=(2Ek/v^2), or
m=(Ep/gh)

Just don't work because I don't have that information. I'm totally lost... And that's all the formulas I can extrapolate from what information they've given me. All I need is a formula to follow, and I can get it from there, thanks muchly.
 
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At 0.05 metres what is the potential energy?

This same energy is converted entirely to ke as it passes through the equilibrium position.

1/2 mv2=mgh
 
rock.freak667 said:
At 0.05 metres what is the potential energy?

This same energy is converted entirely to ke as it passes through the equilibrium position.

1/2 mv2=mgh

I'm not supplied potential, kinetic, or mechanical energy.
 
Serpentia said:
I'm not supplied potential, kinetic, or mechanical energy.

Using the formula, m cancels out. you have g and h. find v.
 
rock.freak667 said:
Using the formula, m cancels out. you have g and h. find v.

Oh, doy, thanks so much. Got it now.
 
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