An experiment using two jars to demonstrate friction
In this experiment we race two jars – one full of water and the other empty (actually it’s full of air). Before racing the jars, take a guess as to which jar will finish first.
- Fill one of your jars with water.
- Put lids on both of the jars. Make sure the lid on the jar full of water is tight.
- Place a three-ring binder on a level floor and start both jars from the top of the ‘ramp’.
Which one gets to the bottom of the ramp first? Which one rolls the farthest? Were you surprised at the outcome?
When the race begins, the jar full of water moves down the ramp faster than the empty jar. This happens because its weight is evenly distributed throughout its volume, thanks to the water inside it. The empty jar’s weight is all in the glass perimeter, so it doesn’t roll quite as fast. But as the jars begin rolling on the flat surface, the greater weight of the full jar causes friction between the jar and the floor as well as friction between the water and the inside of the jar. The full jar slows down, allowing the lighter, empty jar to take the lead!
Advanced notes about the Off to the races science experiment
Friction is a force that occurs between two surfaces in contact with each other, which opposes the motion of one surface relative to the other. It’s the resistance to the motion of surfaces that touch, resistance of a body in motion to the air, water, or other medium through which it travels or to the surface on which it travels. Oil reduces friction. Bodies moving through a vacuum encounter no friction. A sled moves more easily on smooth ice than on rough ground because there is less friction.
The magnitude of frictional force depends on the nature of the surfaces in contact, the amount of force pressing them together, and the roughness of the surfaces. The coefficient of friction is a measure of the degree of roughness between two surfaces, and it can be used to calculate the maximum frictional force that can be expected between them.
Friction plays an important role in our daily lives, as it allows us to walk, drive, and grip objects. However, it can also be a hindrance in many situations, such as when trying to move heavy objects or when designing machinery. Therefore, engineers and scientists are constantly studying ways to reduce friction and improve efficiency in various applications.
Required supplies for the Off to the races experiment
Supplies: Glass jar, Three-ring binder
In-Article Image CreditsAntique glass mason jars via Wikimedia Commons with usage type - Creative Commons License. April 3, 2008
Featured Image CreditAntique glass mason jars via Wikimedia Commons with usage type - Creative Commons License. April 3, 2008