Center of gravity!
Students will
• Understand what center of gravity (COG) means and how to find the COG in different
objects (and even ourselves!)
• Demonstrate that the lower the center of gravity is, the steadier we are, which makes it
more difficult for us to lose our balance
Materials
Included in the Kit:
• Ruler
• Playdough
• Toothpick
• Index Card
• Popsicle Stick
• Pipe Cleaners
• Clothespins
Not Included in the Kit:
• Paper
• Ball (basketball, football, etc…)
• Pen or pencil
Lesson
Hello Scientists! This activity is all about CENTER OF GRAVITY. Have you ever heard of that before?
CENTER OF GRAVITY is the point at which an object is perfectly balanced. Why is it important to know the
Center of Gravity (COG) for an object?
Knowing the center of gravity is important for everything from hanging a picture on the wall to playing
football. We will do an experiment about that later. Did you know even tightrope walkers are able to perfectly
balance on that rope because of their knowledge of the Center of Gravity? What about its use in science and
engineering? When engineers design and build cars it very important for them to know exactly where the COG
is because if it’s too high it can cause the car to be very unstable and it could topple over.
OK, quiz time! Approximately, where is the center of gravity in the human body? In the head? In the knees? In
the belly? The correct answer is in your belly (or intestines)! That is the where the COG of the human body is!
So, your center of gravity is about half of your height up from the ground. So, if you are 60 inches tall, your
center of gravity is about 30 inches above the ground (close to your waist).
But, what happens to your center of gravity when you raise your arms up to the sky? Raise your hands and
reach to the ceiling. Is the center of gravity of your body still the same or is it higher? Your COG has indeed
changed, it is now higher! Now, it is closer to your heart.
What if you roll up in a ball, do you think your center of gravity is higher or lower? Lower of course! Let’s do
some experiments that will help us understand CENTER OF GRAVITY even better!
