What is a pendulum?
A pendulum is an object hanging from a fixed point that swings backwards and forwards when pulled back and released. Imagine sitting on a swing in a park. If someone pulled the swing back and let go the swing would move backwards and forwards and eventually stop without another force to keep it moving. The movement slows because of friction acting between the air and the swing.
Energy transfer and a pendulum
As a pendulum swings gravitational potential energy is transferred into kinetic energy and then back to gravitational potential energy.A pendulum is a great way to demonstrate how energy is transferred.
The swinging movement of a pendulum is due to gravity and the back and forth movements are called oscillations.
What is the period of a pendulum?
A period is the time it takes for a pendulum to swing back into the position it started from. The period of a pendulum increases with pendulum length.
This simple pendulum painting activity is a great way to demonstrate how a pendulum moves.
Pendulum Painting
You'll need
3 wooden garden sticks
Small paper cup
Scissors
String
Paint
Pen
Small container for paint
Water
When you pull back and release the cup it swings like a pendulum. Paint falls from the cup as it moves showing the path of movement.
Instructions
Tie the top of the three sticks together to make a tripod shape.
Check the frame is secure.
Carefully use a pen to make a small hole in the bottom of the paper cup. This is to allow the paint to drip through.
Make two more holes in the cup, one on either side at the top. Thread a long piece of string through the holes and tie like the photo below. The cup needs to be hanging from a single point. Attach the other end of the string to the centre point of the tripod.
Check the cup swings like a pendulum.
The paint needs to be quite thin to fall easily from the cup. Mix one tablespoon of paint with 2 tablespoons of water and stir well.
Pour a little paint into the cup and let the pendulum swing.
Extra challenge
Try swinging with more and less force and observe how the pendulum path changes.
Experiment with a longer and shorter string.
Examples of pendulums
A swing
Grandfather clock
Newton's cradle
Science Concepts
Last Updated on August 6, 2022 by Emma Vanstone
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