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Physicists study matter – all of the “stuff” in the universe and how that “stuff” moves. One of the most famous physicists of all time was Sir Isaac Newton. Sir Isaac is most famous for explaining gravity, a concept we are so familiar with now it seems obvious to us. He is also famous for explaining how stuff moves, his Three Laws of Motion. Today we are going to look at Newton’s First Law of Motion called Inertia.
Newton’s First Law of Motion (Inertia): A still object will stay still unless a force pushes or pulls it. A moving object will stay moving unless a force pushes or pulls it.
Gravity and friction are forces that constantly push and pull the “stuff” on earth. So, when we roll a ball, it slowly comes to a stop. On the moon, where there is less gravity and friction, “stuff” floats, and keeps floating.
In this video, an astronomer demonstrates Inertia:
Here are some good websites that explain inertia or show you experiments to try:
- Experiment: Steve Spangler – Egg Drop
- Experiment: Steve Spangler – Tablecloth Trick
- Experiment: Steve Spangler – The Coin Drop
- Experiment: Bill Nye – Pages of Inertia
- Experiment: Hunkin’s Experiments – Inertia Cartoon
- Physics4Kids: Newton’s Laws of Motion
- Rice University: Newton’s Laws of Motion
- Why Don’t I Fall Out When a Roller Coaster Goes Upside Down?
You can try two Inertia Experiments at home:
For The Tablecloth Trick You Will Need:
Drinking Glasses (non-breakable!)
a Plate (non-breakable!)
a Piece of Frabric or Tablecloth with NO HEM
The items on the tablecloth – the drinking glasses full of water and the plate – are not moving. According to Newton’s law they should stay still unless a force pushes or pulls them. When you pull the tablecloth out from under them friction is a force that causes the plate to move just a little, but since the cloth is slippery it pulls right out, leaving the plate and glasses full of water in place.
For The Egg Drop You Will Need:
Toilet Paper Tube
In The Egg Drop the egg is not in motion, it is at rest. According to Newton’s law it should stay that way. When you slap the pan away you apply force to the pan and it moves, knocking out the toilet paper tube also, but you did not hit the egg so it stays in place. It DOES drop though, since the support of the toilet paper tube is gone gravity acts on the egg and pulls it toward the earth.
In this video see how seat belts and head rests in cars help save lives by using Newton’s First Law of Motion (Inertia):
Here are some books that will help you understand inertia, learn about Sir Isaac Newton or get directions for inertia science experiments:
- Gizmos and Gadgets – Inertia Zoom Ball (pages 9-10); Inertia Coin Magic (page 12).
- Google Preview: Naked Eggs and Flying Potatoes: The Egg Drop (Pages?)
Words to Know:
Physics – The study of matter and motion.
Physicist – A person who studies matter and motion.
Sir Isaac Newton – A physicist from the 16/17th Century who figured out gravity and three laws of motion.
Laws of Motion – Rules that explain how matter, or “stuff” moves on earth.
Inertia – Newton’s First Law of Motion. Every object persists in its state of rest or uniform motion in a straight line unless it is compelled to change that state by forces impressed upon it. SIMPLY: A still object will stay still unless a force pushes or pulls it. A moving object will stay moving unless a force pushes or pulls it.