CENTER OF GRAVITY By: Jordan Young, HannaH Simmons, Nik Schmidt, Renè Chatneuf, Katrina Schmidt, MaryAnne Cavasos

Center of Gravity  An object’s center of gravity is the point at the center of the object’s weight distribution.  For a symmetrical object the center of gravity is at the geometrical center.  For an irregularly shaped object the center of gravity is toward the heavier end.  If an object is moving with rotational motion then it is moving about it’s center of gravity.

Center of Mass  The center of gravity is also called the center of mass.  This is the point of average mass distribution for an object.  An object in outer space where gravity force is almost zero then the object has a center of mass but no center of gravity.  If you threw a lopsided object the center of gravity would follow a parabolic path but the object would wobble because of the distribution of mass.

Locating the Center of Gravity  The center of gravity for uniform object is at the midpoint. Supporting it at that point would support the whole object.  For a suspended object the center of gravity will hang directly below the point of suspension.  The center of gravity for a ring for example would exist where there is no actual material.  A plumb bob can be used to find the center of gravity for an irregularly shaped object.

Toppling  An object will topple when the center of gravity extends beyond it’s support base.  If the center of gravity is above the base the object will remain upright, such as the Leaning Tower of Pisa.  The support base of an object is not always solid, such as a chair.

Stability  It is nearly impossible to balance a pen upright because the base of the support is inadequate for the point but it is adequate for the flat end.  When an object is balanced and any displacement raises its center of gravity it is in a stable equilibrium.  When an object is on its side and its center of gravity is neither raised or lowered with displacement it has a neutral equilibrium.  Any object that hangs with its center of gravity below its point of support it is in stable equilibrium

Stability (cont.)  If a building’s center of gravity is below ground then it is impossible for it to fall over while it is intact.  If the object is heavier than an equal volume of water, it will be more dense than water and sink.

Center of Gravity of People  When you stand erect with your arms hanging at your sides your center of gravity is within your body.  The center of gravity is slightly lower in women than it is in men because women tend to be proportionally larger in the pelvis and smaller in the shoulders.  In children the center of gravity is approximately 5% higher because of their proportionally larger heads and shorter legs.  When you stand your center of gravity is somewhere above your support base which is in the area bound by your feet

Bibliography  Hewitt, Paul G. "Center of Gravity." Conceptual Physics: A High School Physics Program. Menlo Park, CA: Addison-Wesley, Print.