Center of mass

In <a href="/facts/Physics/a7aH2y08">physics</a>, the center of mass of a distribution of <a href="/facts/Mass/HHdc8XmF">mass</a> in <a href="/facts/Space/tq6LUM3C">space</a> (sometimes referred to as the barycenter or balance point) is the unique point at any given time where the <a href="/facts/Weight_function/YNJL7o99">weighted</a> relative <a href="/facts/Position_(vector)/Tpk5d9f2">position</a> of the distributed mass sums to zero. For a rigid body containing its center of mass, this is the point to which a force may be applied to cause a <a href="/facts/Linear_acceleration/UVDmjYvR">linear acceleration</a> without an <a href="/facts/Angular_acceleration/jDv9uzAS">angular acceleration</a>. <a href="/facts/Calculation/MHq42Sjw">Calculations</a> in <a href="/facts/Mechanics/A3yHLQA5">mechanics</a> are often simplified when formulated with respect to the center of mass. It is a hypothetical point where the entire mass of an object may be assumed to be concentrated to visualise its motion. In other words, the center of mass is the particle equivalent of a given object for application of <a href="/facts/Newton%2527s_laws_of_motion/XKzGTXK1">Newton's laws of motion</a>.
In the case of a single <a href="/facts/Rigid_body/THezBlq2">rigid body</a>, the center of mass is fixed in relation to the body, and if the body has uniform <a href="/facts/Density/92p6hh9I">density</a>, it will be located at the <a href="/facts/Centroid/H6dDbg0h">centroid</a>. The center of mass may be located outside the <a href="/facts/Physical_object/WhqjK6xo">physical body</a>, as is sometimes the case for hollow or open-shaped objects, such as a <a href="/facts/Horseshoe/5gXPTqFB">horseshoe</a>. In the case of a distribution of separate bodies, such as the <a href="/facts/Planets/rbPjE6Bx">planets</a> of the <a href="/facts/Solar_System/QIcLSazQ">Solar System</a>, the center of mass may not correspond to the position of any individual member of the system.
The center of mass is a useful reference point for calculations in <a href="/facts/Mechanics/A3yHLQA5">mechanics</a> that involve masses distributed in space, such as the <a href="/facts/Momentum/TTkGv5eY">linear</a> and <a href="/facts/Angular_momentum/7TuSVFxq">angular momentum</a> of planetary bodies and <a href="/facts/Rigid_body_dynamics/ajbkweF2">rigid body dynamics</a>. In <a href="/facts/Orbital_mechanics/oB3tqNG9">orbital mechanics</a>, the equations of motion of planets are formulated as <a href="/facts/Point_mass/4MPToN8W">point masses</a> located at the centers of mass (see <a href="/facts/Barycenter_(astronomy)/Fw9renao">Barycenter (astronomy)</a> for details). The <a href="/facts/Center_of_mass_frame/gw4QHPwq">center of mass frame</a> is an <a href="/facts/Inertial_frame/1U6TrdG3">inertial frame</a> in which the center of mass of a system is at rest with respect to the origin of the <a href="/facts/Coordinate_system/Mtd0q4SP">coordinate system</a>.

Center of mass open-in-new

Center of mass