Extreme Science: Center of Gravity - Spokane, North Idaho News & Weather KHQ.com

Extreme Science: Center of Gravity

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Center of Gravity

What you will need:

A) Finding the center of gravity of an object:

  1. Yardstick or other straight objects.
  2. Roll of tape

B) Balancing forks

  1. Two (2) forks
  2. Quarter
  3. Glass

C) Can’t get up

  1. Chair
  2. Willing volunteer

Procedure:

A) Finding the Center of Gravity:

To find the center of gravity of an object such as a yardstick, simply hold your hands just less than 3 feet apart with your index finger pointing forward and place the yardstick on your index fingers. Slowly move your hands together. As you do, the yardstick will find its’ own balance.

What is going on?

As you slide your hands together, the weight of the yardstick will cause friction between your hands and the yardstick. You will notice that the yardstick will slide on one hand while it seems to “stick” to the other hand. Eventually, there will be more mass hanging out past one hand than the other causing more friction due to the weight of the yardstick on this particular hand. At that moment, the yardstick will “stick” to the hand having more friction and the other hand will be allowed to slide since there is less friction between that hand and the yardstick. This action will continue back and forth as you move your hands together due to the “center of gravity”


B) Balancing Forks:

Carefully place a quarter between two outer tines of a dinner fork. Now carefully force another fork in with the tines overlapped with each other as well as the quarter as shown.

What is going on?

Although this looks impossible, the forks and quarter will balance on the edge of the glass as long as you place it to where the center of gravity is right on the edge of the glass. Since the tines of the fork and most of the quarter are on one side of the balance point (the edge of the glass) and the rest of the quarter and the forks handles are on the other side of the balance point, it is possible to get this to place this so that the center of gravity is directly over the edge of the glass allowing it to balance over the edge of the glass.


C) Can’t get up:

Using a regular chair, have your volunteer sit down with their feet on the floor in front of the chair. Place your palm (or thumb) on their forehead and do not let them lean forward. Ask your volunteer to try to stand up. As long as you do not allow them to lean forward, they will not be able to get up out of the chair.

What is going on?

In order to get up out of a chair, you must lean forward to get your center of gravity over your feet. When you hold your volunteers head so that they cannot lean forward, you do not allow them to shift their weight or center of gravity making it impossible for them to stand up.

Try this:

Stand with your back to the wall making sure that your heels are also touching the wall. Now try to bend over and touch your toes without falling on your face! Typically, when we bend over to touch our toes, we shift our midsection backwards to maintain our center of gravity. With our backs and heels to the wall, we cannot shift our weight and therefore cannot touch your toes without falling over.

- Radical Rick, Extreme Science

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