Center of Gravity
What is the Center of Gravity?
The point through which
the whole weight of the
body acts or the point at
which weight is evenly
dispersed and all sides are in
balance.
Gravity- this invisible force that pulls
objects toward one another. And one of
the things that gravity does is pull us
toward the earth.
Locating the center of gravity
For a symmetrical(regular/uniform) object
the center of gravity is located at the

geometric center of the object.

If a figure can be folded or divided into half so that
the two halves match exactly then such a figure is
called a symmetric figure
CoG of an irregular shape

Find the CoG of an irregular shaped
lamina
Pin held by
clamp
a
b
c
b
c
a
c
a
hole
plumb line
b
Locating the center of gravity
• The
center of gravity of irregular objects is at the
intersection of the three lines.
• To
locate center of gravity in irregular objects.
Ans: Use a plumb line, suspend the object from various
points (3 or more) and trace the plumb line’s location
each time and find the intersection of the traced lines.
What object shape will be the most stable
(least likely to tip over)?
• Objects with wide bases and low centers of
gravity are more stable and least likely to tip over
The orientation of an object can change the position or height of
its centre of gravity and affect its stability.
• When will an
object topple
over?
• If an object is
tilted it will
topple over if a
vertical line
from its center
of gravity falls
outside its base.
Factors Affecting Stability
Three primary factors:
1. Size of the base of support.
2.
Relation of the line of gravity to the base of
support.
3.
Height of the center of gravity
Why do we care about the center of gravity?
Stability!
• Stability is important when designing vehicles and
particularly tractor because farmland is often steep on
hillsides.
How to be MORE stable
1. The LOWER your
centre of gravity the
MORE STABLE you
will be
The Centre of Gravity is at a
different height
How to be MORE stable
The LARGER the
area of your Base of
Support, the MORE
STABLE you will be
The Base of Support
is larger
The Base of Support
is smaller
STANDARD GRADE
How to be MORE stable
The CLOSER your
centre of gravity
is to the centre of
your base of
support, the
MORE STABLE you
are.
The Line of Gravity falls
outside of the centre of
the Base of Support
SKILLS & TECHNIQUES
SKILLS & TECHNIQUES
STANDARD GRADE
Point of Balance
Why is an object balanced at the
center of gravity?
• When an object is supported at it’s center of gravity
there is no net torque acting on it, and it will remain
in static equilibrium.
•Torque-turning force
Three types of equilibrium
•Unstable – when an object is tilted and its center of
gravity falls outside of its base
•Stable – when an object is tilted and its center of
gravity rises, but return to original position.
•Neutral – when an object is tilted and the CG neither
rises nor falls
Question
1.Why is the middle seating more comfortable in a bus
traveling along a bumpy road?
• The bus tends to rock about its CG.
The closer your seat is to the
CG, the less up and down motion as the bus rocks.
2. An
unsupported object will topple over when its
center of gravity
a.lies
outside the object.
b.extends beyond the support base.
c.is displaced from its center of mass.
d.lowers at the point of tipping.
Answer: B
Question
3. When
a stable object is made to topple
over, its center of gravity
a.is at first raised.
b.is lowered.
c.plays a minor role.
d.plays no role.
Answer: A