Why does a grandfather clock have a pendulum

It only takes a minute to sign up. Connect and share knowledge within a single location that is structured and easy to search. How do grandfather clocks keep going? The pendulum is what makes the clock go. However, the pendulum will slow down due to friction. What energy source keeps the pendulum from eventually stopping?

The premise of your question is incorrect: in fact, the pendulum is what keeps the clock from running! And the clock keeps the pendulum running! A clock is essentially a motor: a device that uses energy from some source to drive the hands of the clock around and around. The source of the energy varies; it could be a tightly wound spring, or a weight dropping down after being raised to some height.

The energy is dissipated in the friction in the various gears that are used to reduce the speed of the motor for the different hands. The speed of this motor would depend only on the friction in the various gears The role of the pendulum is critical. In part of its motion back and forth, it stops the gear train from moving.

As the pendulum moves further in its swing, it releases a tooth of the gear, which rotates a little until another part of the pendulum catches another tooth. So each swing of the pendulum allows the clock "motor" to rotate only a fixed number of teeth usually one tooth exactly. Here's a simple example of an escapement :.

The anchor is connected to the pendulum and latches to the escapement gear teeth. The anchor is roughly the shape of an upside-down U. This provides the constant movement of the second hand of the clock.

The minute and hour hands of the clock turn due to the same basic process, but the gears powering the minute and hour hands turn after many more oscillations of the pendulum. Thus, the pendulum becomes the means of a consistent release of the potential energy stored in the weights. A weight is attached to a chain that wraps around the gear farthest from the escapement gear; this weight provides potential energy to the pendulum, maintaining its swinging at a constant rate.

The unwinding of the chain around the gear and the subsequent sinking of the weight represents potential energy loss of the weight.

If the gear connected to the escapement anchor was attached to the drum, every 60 seconds depending on the length of the pendulum the drum would complete one full revolution.

This would translate to a clock that needs to be wound every 20 minutes and only has a second hand [4]. Gear ratios overcome this problem. For each of the time keeping pieces — hour hand, minute hand, and second hand — a corresponding gear must be turning at an appropriate rate.

The ratio for seconds to minutes as well as minutes to hours will be , while hours to the traditional half-day clocks will be Further ratios are necessary to create a desirable winding interval or an interval that is once daily or weekly for ease in maintaining show series of gears here. Usually, several gears are placed between the weighted gear and the escapement gear.

With more gears separating the two ends, the weighted gear moves more slowly, causing the weight to drop and lose energy at a slower rate. Though the ratios of the gears seem easy enough to understand, it becomes difficult to align each gear to access a hand on the face of the clock. This problem is usually solved by utilizing tubular shafts to run the movement of the hands of the clock one within another [4].

However, even with the tubular shafts, arranging the gear works remains a challenging task Fig. Figure 1: Gears are arranged with appropriate ratios to ensure proper revolution. The setting mechanism is generally a small lever connected to a gear to pull the gear out of alignment with the others.

Contrary to common belief, the Long Case clock was not created to house a long pendulum. Watch your cell phone time as soon as it advances to the next minute on whatever hour it is on, set the minute hand on the grandfather clock to that location. The Grandfather clock pendulum adjustment is done by turning the nut at the bottom up to speed up the grandfather clock or down to slow the grandfather clock.

Move the nut up or down depending if it is slow or fast about a full turn for a minute a day. If your grandfather clock is slow or fast, the speed is dictated by this adjustment. It is always easier for the clock to begin slow and then start raising the pendulum nut so the clock will gradually run faster until the correct time is achieved.

That it tells time for us is convenient, but doesn't cost energy in principle. An ideal mechanical clock no friction would cost no energy to run, only energy to start. Newton's first law of inertia tells you that if you pull a pendulum and let it go, it will continue to go back and forth until friction forces rob it of its energy initially supplied by you to lift the pendulum arm in the first place.

That said, here's a brief description of how mechanical clocks work:. Mechanical clocks work by having a weight connected to a string, then wrapped around the shaft of the first gear. The weight constantly pulls downwards on the gear, trying to turn it. There is generally an additional piece of wood that sticks in one of the gear teeth preventing it from turning holding the weight back which is connected to a pendulum. The pendulum's length is set so that it swings from one side to the other in 1 second and each time it gets to the opposite side it lets the gear tooth turn once.

The energy to swing a pendulum in a mechanical clock can be any form, though commonly mechanical clocks will use a spring or a weight. If a spring is compressed, it will do work, like move the pendulum, as it decompresses.

Likewise, a weight will want to fall towards the ground, and this can also do work.