Tie the small weight to one end of an 80 cm piece of string. Measure 75 cm from the weight and tie the other end of the string to the dowel or stick. You should try to have as close to 75 cm of string from the weight to the stick as possible. Place the backs of two chairs a little over 75 cm apart, and place the stick over the two chair backs as shown. Pull the weight to one side and let it go. You have made a simple pendulum.
In order to study pendulums, there are a few terms you will need to understand.
Conclusion:
· First, the length of the pendulum is the distance from the point where it is suspended to the center of gravity of the weight. In this pendulum, the length is 75 cm.
· Second, the period of the pendulum is the time it takes the pendulum to make one complete swing from one side to the other and back again.
· Third, the frequency of a pendulum is the number of periods or complete swings per second.
· Finally, the amplitude of a pendulum is the distance from the low point or center of the pendulum to the highest point of the swing.
Concept in daily life
Wall Clocks
Pendulums in clocks have a weight called bob suspended by a rod made out of either metal or wood. The bob is usually a smooth disk with a lens-shaped cross section and is made as heavy as possible to reduce air resistance and improve accuracy of the clock.
Seismometers
Motions of the ground, including those of seismic waves generated by seismic sources such as earthquakes and volcanic eruptions, can be measured by seismometers. In older seismometers, a pendulum with a stylus at its bottom was connected to a frame. During an earthquake, for instance, the heavy bob does not move due to its inertia while its frame does. This causes the stylus to form a pattern on either a smoked glass or paper which would be according to the Earth’s movement.
