| MadSci Network: Physics |
It sounds like you did some very good experimental work! I will try to clarify your results:
The 'tipping' tendency of a body depends on two factors- the height of the center of gravity (CG) and the size of the base of the body that touches the ground.
The center of gravity can be thought of as the point (usually) within the body which would balance the body in all three axes. Imagine a block of wood 2 x 4 x 24". The center of gravity would be at a point 1 x 2 x 12 inches from a corner of this block. A body will react the same way if you assume all of the mass is located at the CG.
Stand the block up on the 2 x 4 face: The CG will be located 12" above the ground and the block will have a large tendency to tip because the height of the CG (12) is much greater than the base- 2 or 6 inches. You can see that the block would tip much easier over the 2 inch side compared with the 4 inch side.
Ok, now lay the board down on the 4 x 24 face. The CG will only be 1" from the ground (one half of 2"). The base (4 x 24")will be much larger than the height of the CG. Therefore, the block will have no tendency to tip.
The CG can be calculated for complex objects, such as cars. A car designer wants to keep the CG low compared with the wheel base (the square formed by the four tires on the ground). This reduces the tendency for the car to tip, on inclines or going around curves.
Notice that the weight of the body does not matter! [note added by MadSci Admin: this assumes that the density is constant throughout the body.] It is all in the geometry of the body, the relationship of the CG height to the base on the ground.
Keep up the experiments!
-Jay Shapiro
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