Stability and Center of Mass

(f) describe qualitatively the effect of the position of the center of mass on the stability of simple objects.

As in most occasions, the center of mass and the center of gravity of an object act at the same point, we can consider the effects of center of gravity on the stability of an object.



The center of gravity of an object affects its stability in two ways.

  1. Position of center of gravity
The lower the center of gravity of an object is, the stabler it is. Objects with higher center of gravity are easier to topple than objects with lower center of gravity. In the following picture, car 1 is less stable than car 2, because it has a higher center of gravity


  


   2. Area of base

An object with a big base area is less likely to fall or topple over, than an object with a small base area. You might have observed this in your everyday life e-g tall glassware like mugs with small base areas fall over easily compared to mugs with a larger base area.


Furthermore, these two factors combine to decide the stability of an object. An object would fall over, if it's center of gravity does not pass through its base when it is tilted. Look at the following picture.



When the first car is tilted, its center of gravity no longer acts through its base. Therefore it would topple over. But the second car would not topple, as its center of gravity still acts through its base.

Same is the scenario with the red bus.

From here, we can deduce that.
  1. If the base area of an object is large, it is less likely to topple over because the center of gravity would still act through the base even when the object is tilted.
  2. If the center of gravity of an object is low, it is less likely to topple over because the gravity would still act through the base even when the object is tilted.

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