6. From its discovery around 1602
by Galileo Galilei, the regular
motion of pendulums was used for
timekeeping, and was the world's
most accurate timekeeping
technology until the 1930s.
The word 'pendulum' is new
Latin, from the Latin pendulus,
means 'hanging‘
7. The simple gravity
pendulum is a weight
(bob) on the end of a
massless cord
suspended from a
frictionless pivot.
When given an initial
push, it will swing
back and forth at a
constant amplitude.
8. The period of swing of a simple
pendulum depends on its length, and
the local strength of gravity.
If the amplitude is limited to small
swings, the period (T) or the time
taken for a complete cycle of a
simple pendulum, is:
9. For small swings, the
period of swing is
approximately the same
for different size
swings. So, the period
is independent of
amplitude.
This property, called
isochronism, is the
reason pendulums are so
useful for timekeeping.
Successive swings of the
pendulum, even if
changing in amplitude,
take the same amount of
time.
10. External factors:
Temperature
The largest source of error in early
pendulums was slight changes in
length due to thermal expansion and
contraction of the pendulum rod with
changes in ambient temperature.
12. External factors:
Gravity
Pendulums are affected by
changes in gravitational
acceleration, which varies by as
much as 0.5% at different
locations on Earth, so pendulum
clocks have to be recalibrated
after a move
