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Explore the concept of center of mass in physics, how to find it, its impact on balance, stability, and equilibrium. Learn about resultant gravitational forces, torque, and more.
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IHSAN DOĞRAMACI FOUNDATION BILKENT ERZURUM LABORATORY HIGH SCHOOL CENTER OF MASS Cemre Çise KADIOĞLU 102
KEY WORDS Center of gravity, plumb line Weight, torque Resultant-gravitional forces Stability Balance Equilibrium Turning effect
What is centre of mass? • The small forces act like a single force at G. This means that they have the resultant force at G. • The resultant force is the stick’s weight. • G is the centre of mass. Gravitional forces on particles of stick
What is centre of mass? • Centre of mass of a body is the body that moves as though all of the mass were applied there.
Finding centre of mass • If the object is uniform, for example a meter stick, the center of mass will be at the exact geometric center. • But, if the shape is irregular we use plumb line. • Draw lines from each vertex along the plumb line by assuming that the point is on that line • After drawing the lines the centre of the mass will be on the intersection point of these lines. G Intersection point-Centre of mass
Finding the centre of mass • But, if the shape is irregular we use plumb line. • Draw lines from each vertex along the plumb line by assuming that the point is on that line • After drawing the lines the centre of the mass will be on the intersection point of these lines. Intersection point-centre of mass Plumb line
Balancing unequal masses are again about centre of mass • For example, • The bus is heavier than the car so they’re not in balance. M2 M1 d2 d1
In order to balance the system, we should change their distances to the support. • Now they’re in balance. d1 d2 m1.d1=m2.d2
Stability –Equilibrium • If an object isn’t moving and remainig same, the object is stable. • State of rest or balance due to the equal action of opposing forces is called equilibrium. • When the object is stable it’s also in equilibrium which means the forces acting on the object and the forces turning effects are in balance.
Stability-Equilibrium Will turn to its original position Small force will turn it over Will definetely fall over before another force is applied
Types of equilibrium • There are three states of equilibrium,
Stable equilbrium • The objects that have wide base also have the lower centre of mass. • The lower the centre of mass is, the more stable object is. • So it’s more difficult to fall over an object with wider base.
Unstable equilibrium • The objects that have very little base, have high centre of mass. • And if these objects are tilted the centre of mass immediately passes beyond the base. • So they’re not stable and it’s easy to fall these objects over.
Neutral equilibrium • The objects that are in neutral equilibrium stay where they’re lefted. • When moved, it changes the position. • Wherever they stay, their center of mass is always over their base.
References • Complete Physics for IGCSE • http://dev.physicslab.org/Document.aspx?doctype=3&filename=RotaryMotion_CenterMass.xml • http://dictionary.reference.com/browse/equilibrium • http://en.wikipedia.org/wiki/Center_of_mass • http://eteach.engr.wisc.edu/meibom/espp/slides/espp.ppt • http://solar.njit.edu/~cdenker/physics111_lecture08.ppt