manual

16
A body is balanced when the sum of all the forces that
act on it is zero.
stable equilibrium
support
(pivot) point
center of
gravity
NOTE: You can use
the cardboard arms
from the “Rolling Uphill”
experiment instead of a belt.
cardboard
arms
Why is equilibrium
possible in this experiment?
The finger is on a support
(pivot) point that is higher
than (and vertical to) the
structure’s center of gravity,
which is near the buckle.
For example, a pencil laid across your fingers won’t fall off because the
fingers support it by opposing the forces of gravity that attract all things
toward the center of the Earth. Keep in mind that if your fingers weren’t
exerting an upward force, the object would fall down.
Every object has its center of gravity, which is the point at which you can
imagine its weight being concentrated.