# Homework Help: Investigation: Mechanical Energy in a Pendulum

1. Jul 7, 2008

### trossi

1. The problem statement, all variables and given/known data
a pendulum was set up and measurements were made to enable the mechanical energy to be calculated at the start position and the lowest point of the pendulum's swing. The mass of the pendulum bob was determined on an electromic scale, and its diameter was measured using calipers. The initial hieght was measured using a metre stick. At the lowest point of its swing, the pendulum bob broke a photogate (spart or light generator) light beam. The time interval that the light was interrupted was recorded on an electronic timer attached to the photogate.

Mass of pendulum bob: 240.3 g
Diameter of pendulum bob: 3.50 cm
Initial height of pendulum bob: 48.0 cm
Length of pendulum string: 2.14 m
Time interval of photogate light interruption: 11.8ms

2. Relevant equations
For my report I need to calculate mechanical energy at the start position and at the lowat point of the pendulum's swing.
I also need to include:
- a conclusion as to whether or not the pendulum demonstrates the law of conservation of energy
-my calculations of the efficiency of the pendulum as a mechanical machine

I'm not sure how to approach this question

2. Jul 7, 2008

### dynamicsolo

What is the definition of mechanical energy?
What types of energy are included in it?
How do you calculate the values of those energies?
What measurements have you made that will help you find the quantities needed for calculating those energies?

One of the things you are asked to do is to compare the mechanical energy at the moment when you released the bob and at the moment when it was at the bottom of the swing, crossing the photogate (why do you make a time measurement then?).