# Pendulum Question?

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1. Mar 28, 2015

### aizeltine

1. The problem statement, all variables and given/known data

For the conservationofenergy,calculate the starting height of the bob. This is done with some trigonometry and is
∆h=L−Lcosθ
Calculate the initial potential energy of the pendulum for each of your starting angles.Now, using the diameter of the hanging mass (2 cm),and the time it took to pass through the photogate (***), calculate the velocity of the pendulum bob at the bottom of its swing.Using that velocity, calculate the kinetic energy of the pendulum bob.
•Compare the initial potential energy to the kinetic energy of the bob for each angle. Find the percent difference for each. Was energy conserved?
•If you let the pendulum continue to swing,it will eventually slow down and stop. Does this violate the conservation of energy?Why or whynot?

*** THE IMAGE OF THE DATA TABLE CAN BE SEEN AT :https://www.chegg.com/homework-help...y-using-data-using-diameter-hanging--q7017035

I ATTACHED THIS IMAGE BELOW SO U DONT HAVE TO CLICK ANY LINK.

2. Relevant equations

∆h=L−Lcosθ, ... Diameter =2 cm
3. The attempt at a solution
Ok. Well, Im not really sure what L means in terms of my data..and the other questions i dont really know, im a chem major and dont know anyhting about physics. I need help and guidance with the calculation questions. and the theoretical questions, i dont have any idea lol

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2. Mar 29, 2015

### PWiz

$l$ is the length of the string. Draw a diagram and you should be able to see why $\delta h$ is calculated using that expression. With the values given in the table, you should be able to compute the change in potential energy of the bob after it is released and reaches the bottom of the swing.

Does any equation come to your mind for calculating the velocity at the bottom? Remember that you have to take experimental error into consideration when using the values in the table.
Hint: This motion can be approximated to simple harmonic motion (the angle is small enough). Try integration.