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11.1 Finding the centre

How does a tightrope The centre of mass
walker keep balanced? All objects have mass. This mass is spread throughout the volume a

substance/object fills. In science, to make our lives easier when observing
phenomena and making calculations, we make assumptions. One of the
textbooks nis edu kz
major scientific assumptions we make is that ALL the mass of any object/
substance is concentrated in a single point. We call this the object’s
centre of mass. In most situations, this centre of mass is also the object’s
centre of gravity.
All objects have a centre of mass, and the force of gravity acts on mass on
the Earth. Imagine a triangular object. If the triangle is divided into many
imaginary small parts, then for each part there will be a force of gravity
acting. All these forces are directed in the same direction – downwards.
And all these forces can be substituted by a single force, and the centre of
gravity can be taken as a point of application of that force. That is a centre
of mass, and the mass of the whole object is assumed to be located there.

ACT Suspend a 2D (2-dimensional) regular triangle made of cardboard by
a strong thread from at least 5 different points. Try to find its centre of mass.
Explain the process you chose.

pin ACT Suggest a method for finding the centre of gravity of other 2D,
regular-shaped objects, e.g. a regular square, a parallelogram and a circle.

Centre of mass of an object with an
plumb line irregular shape
To find the centre of gravity for such a figure it is necessary to suspend it by
freely
hanging different points several times and draw vertical lines as it is suspended. The
card shape intersection point of all these lines is the centre of mass of the figure.

retort stand bob INV Find the centre of gravity of an irregular-shaped, 2D figure made
of cardboard.

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