Clocks and Watches. Pendulum Clocks. A pendulum oscillates with a frequency of:. g is gravitational acceleration R is the length of the pendulum (pivot to center of mass ) Frequency does not depend on weight of the Bob g = 32 ft/s 2 on earth. R. How fast would a 1 ft pendulum swing?.
Clocks and Watches
A pendulum oscillates with a frequency of:
g is gravitational acceleration
R is the length of the pendulum (pivot to center of mass)
Frequency does not depend on weight of the Bob
g = 32 ft/s2 on earth
Freq. = 0.9 cycles/sec. = 9 cycles/10 sec.
g = 32 ft/s2 on earth
The torque of the gears keep the pendulum going.
The gears get energy from the potential energy of the weight or spring in the clock.
Winding the clock raises the weight or tightens the spring.
The escapement ensures that the energy is released in small increments over a long period of time (e.g. daily or weekly).
The pendulum length determines the frequency of the tick-tocks.
When watching this animation, notice that the gear’s tooth gives a little push to the pendulum so that the pendulum continues to oscillates.
The escape tooth slides across the pallet, exerting a small force on it. This small force exerted each cycle keeps the pendulum moving.
This is a clock with only a second hand:
This axle is rotating
Or 5.2 times slower.
Every 5.2 minutes
the Weight wheel rotates once.
The pendulum oscillates at two cycles/sec
Period = ½ second.
Second hand is directly connected to the
Replace pendulum with a small hair spring and balance that oscillates at a certain frequency if regularly energized.
The hairspring coils and uncoils. The hairspring and balance are made to oscillate at a specific
frequency. The hair spring is made from
an alloy that can take the constant coiling and uncoiling.
Watches are Energized with a main spring instead of weights.
Springs store energy:
F = k * x
PE spring = ½ k * x2
k is spring constant (stiffness)
x is the amount of displacement or how tight the spring is wound
As the spring slowly is allowed to unwind, it does very small increments of
Work on the clock.
An Oscillating Weight moves as the wearer’s wrist moves.
The mainspring is automatically wound.
Plan vs. Elevation View of a clock works