What is the difference between center of gravity and center of mass?
An unconstrained object (no axle or pivot) on which there is no net force will rotate about a point called the center of mass.
- The center of mass remains motionless while every other point on the object undergoes circular motion around it.
- The center of mass is the mass-weighted center of the object.
- The distribution of an object's mass is balanced around its center of mass.
The center of gravity is the point at which the resultant torque due to gravity disappears.
- Gravity acts on every particle in the object, exerting a downward force of magnitude
#m_ig#on a particle #"i"#.
- The gravitational torque is found by treating the object as if all its mass were concentrated at the center of mass .
- The point at which gravity acts is called the center of gravity
- The magnitude of the gravitational torque on a particle is
#abs(tau)=m_igd_i#where #d_i#is the moment arm
- An object will balance on a pivot only if the center of mass is directly above the pivot point. Otherwise, the gravitational torque will cause the object to rotate.