Center of Gravity

Question: 

What happens when the center of gravity of a person or object is modified?

Hypothesis:

If the center of gravity is modified, then the ability to perform tasks such as standing up, bending over, and balancing will be affected.
Picture
Materials:
  • Binder clip(s)
  • Chair
  • Pencil
  • Pencil Top Eraser
  • Plastic Birds and Stands 
  • Sharpie
  • Sturdy Wall

Safety Procedures:

Touch Your Toes?- Don't stretch too far.
Power of Thumb- Do not push your thumb hard against the person's forehead.

Procedure:


Shifting Center of Gravity:
  1. Put the bird on the stand and see if it balances.
  2. Next put the binder clip onto the bird's tail.  Note the effect.
  3. Now replace the bird with the pencil and balance it on the stand.  
  4. Add the pencil top eraser to the pencil.  
  5. Balance the pencil and note the effect.

Touch Your Toes?:
  1. Have someone stand against the wall, and someone else stand in the open.
  2. Have both people bend forwards and touch their toes without moving their feet or bending their knees.

Power of Thumb:
  1. Put a chair against a sturdy wall.
  2. Have someone sit in the chair so that their feet touch the floor.
  3. Ask them to stand up.
  4. Have them sit back down.
  5. Put your thumb on the person's forehead. 
  6. Ask them to stand up again.

Special Needs:
Chair
Sturdy Wall - People and a chair will be leaning against it.

Watch us in action:

The Science Behind It:

  1. In Shifting Center of Gravity, the bird balances because it has weights in the tips of both wings, causing the center of gravity to be at its beak.  When the binder clip is added, the center of gravity shifts towards the tail, causing the bird to fall.  The center of gravity is always the balancing point of an object or person.  Where the center of gravity is depends on the distribution of weight in an object.  The center of gravity is normally at the center of the object, but when the weight of an object is unevenly distributed, the center of gravity is changed.  In the example with the pencil, the same pencil balances in different spots because when the eraser is on the pencil, the weight is unevenly distributed, causing the center of gravity to be modified.
  2. In Touch Your Toes?, the person against the wall cannot touch their toes without falling over, because when you bend over to touch your toes, your hips need to shift.  Your hips need to shift to redistribute your weight, so you don't fall over.  The person who is out in the open can redistribute their weight, so they do not fall over.  When you lean over to touch your toes, your center of gravity should be over your toes.  When leaning over to touch your toes when you're against a wall, your center of gravity is not over your toes, causing you to fall. 
  3. In Power of Thumb, the person cannot stand up when someone's thumb is against their forehead because when you stand up, you lean forward to redistribute your weight so that your center of gravity is over your toes.  When someone's thumb is on your forehead, you cannot lean forwards, so you cannot stand up.

Conclusions:
We accept our hypothesis.  We stated that when the center of gravity is modified, it will affect a person or object's ability to do certain things.  These things include standing up (Power of Thumb experiment), and balancing (Touch Your Toes? and Shifting Center of Gravity experiment).  In Shifting Center of Gravity, the more weight you add, the more the center of gravity moves to the side with the most weight.  In Touch Your Toes?, the inability to redistribute your weight stops you from touching your toes without falling over.  Finally, in Power of Thumb, the inability to lean forward stops you from redistributing your weight so you can stand up.  Over all, the center of gravity is the point where all of the weight of an object appears to be focused.  If an object is balancing so that it can move freely, its center of gravity is always directly below the point of its suspension.  An object can be balanced on a sharp point placed directly beneath its center of gravity.  The concept is sometimes useful in designing structures such as buildings and bridges, or in predicting the behavior of a moving body when it is acted upon by gravity. 

About Catherine

Catherine is a 10 year old girl who loves watching and playing hockey, playing soccer, and playing the violin. She has a big imagination and likes to read and write. Her favorite subject is science. Catherine has known Abbey since third grade.

About Abbey

Abbey is a 10 year old girl who is short and proud of it!  She loves playing the piano, writing, and goofing around.  Her favorite subject is a tie between reading and writing.  Abbey has known Catherine since third grade.