1. Center of Gravity

2. Throwing a wrench into parabolic motion

3. Center of gravity
Definition: The point located at the object’s average position of weight.
For a symmetrical object, this is the geometric center of the object.
For a non-symmetrical object (such as a wrench), the center of gravity is towards the heavier end.

4. Motion of a non-symmetrical object
For an object that is non-symmetrical, or has varying density that is in motion, the center of gravity will follow the path as discussed earlier this semester.
The rest of the object will rotate about the center of gravity.

5. Location of the CG
The location of the CG does NOT have to be a location on the object.
Example

6. Toppling
Activity: we are going to hang a plumb bob from a box and increase the incline of the surface the block sits on.
Where is the location of the plumb bob in reference to the base of the box when it topples?

7. Leaning tower of Pisa

8. Activity
Stand exactly two foot lengths away from a wall and place a stool between you and the wall.
Bend over with a straight back and let your head lean against the wall.
Lift the stool off the floor while your head is STILL on the wall.
Then attempt to straighten up without bending your knees.

9. Tails What is the purpose of a tail for an animal?
It allows for an animal to shift its center of gravity and increase its stability

10. CG of people
When standing up straight, a human’s average CG is about 2-3 cm below our belly buttons.
It is slightly lower for women because women tend to have smaller shoulders
It is slightly higher for children because of larger heads compared to their shorter legs at that age.

11. CG for people When you change your position, your CG changes as well.
Your CG is always somewhere above your support base.
That is why you are more stable with your feet shoulder width apart than standing on one leg.

12. Learning to walk
When learning to walk, a baby needs to learn to coordinate the position of their CG with their supporting foot when making a step.
Pigeons bob their head to make up for this.

13. High Jump
Doing the “Fosbury flop” in high jump, jumpers change their CG to below the bar while their body is able to pass over the bar.