6.9.2 Understanding Stable Equilibrium and the Center of Gravity

Question 1

Understanding Stable Equilibrium and the Center of Gravity

Answer 1

• Gravity acts on complex objects as if they were concentrated at a single point called their center of gravity. In a uniform gravitational field (such as on the surface of the Earth), this point coincides with the center of mass.
• An object hanging from a point is in static equilibrium if its center of gravity lies either directly above (unstable equilibrium)or below (stable equilibrium) the support point.
• An object resting on a surface is in stable equilibrium if its center of gravity lies above its base. If its center of gravity lies beyond its base, it is not in equilibrium at all

Question 2

Which of the following statements concerning equilibrium is not correct?

Answer 2

An object is in stable equilibrium if a small displacement or disturbance acts on the object in such a way that the object does not return to its equilibrium position.

Question 3

Which of the following statements about stability is not correct?

Answer 3

A hanging object with a center of gravity below the support point can be brought into stable equilibrium by lowering its center of gravity.

Question 4

Consider the gravitational torque on a body of arbitrary shape. Assume that the body is small in size and that the gravitational torque is the same at every point in all particles of the body. Which of the following statements about the center of mass or the center of gravity is not correct?

Answer 4

The center of mass must be within the physical structure of the object.

Question 5

The center of gravity of an object ________________________.

Answer 5

is always at, directly above, or directly below the point of suspension when the object is in equilibrium and supported or suspended at a single point.

Question 6

The center of mass and the center of gravity of an object coincide if ________________.

Answer 6

the acceleration due to gravity is constant

Question 7

Which of the following statements concerning unstable equilibrium is not correct?

Answer 7

The center of gravity of an object resting on a surface must not lie above the base in order for it to be in stable equilibrium.

Question 8

How many sides of the book provide bases in which a hardbound textbook is in stable equilibrium and unstable equilibrium? The textbook is 9.5in x 7.5in x 0.5in. and is resting on a surface.

Answer 8

2 stable and 4 unstable

Question 9

A body has greatest stability when ______________________.

Answer 9

its base is large.