• Mickey Mouse Clocks: Look at the workings of the clock and how one gear turn another.
• Levers: How can you balance weights along a ruler?
• Gears: Let's look at eggbeaters, hand drill and cork screw
• Inclined plane: How can you make it easier to lift a piano onto a truck?
• Pulleys: Do pulleys help us to lift heavy objects?
• Pendulum Clock: Make a pendulum clock with 24.8cm of string and an object tied to the bottom.
• Colouring competition: Colour in any of the machines: levers, gears, inclined plane or pulleys.

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How do gears work?

Each of the gears in a clock is simply a wheel and axle with teeth. The teeth of one gear fit between the teeth of another gear. When one gear turns the other can be made to turn faster, slower or in a different direction. The gears in the clock allow the three hands to move around the face of the clock at different speeds. The wheel that is moved first is called the driving gear. Usually the driving gear is moved by a person or a mtor. In a bicycle it is moved by pedalling, while in the eggbeater the driving wheel is moved by the handle. The wheel that is moved by the driving gear is called the driven gear. In a hand-operated egg beater there are two driven gears.

Making gears go fast or slow

Different sizes and arrangements of gears are used to make wheels turn faster, slower or in different directions. A large driving gear makes a small driven gear move faster, but in the opposite direction. Hand-operated eggbeaters and drills use this combination of gears to make them spin quickly. A small driving gear makes a large driven gear move slower but in the opposite direction. This arrangement acts as a force multiplier. It is used to move large loads with a small effort. This arrangement in used in cars to allow them to climb hills or gather speed quickly. It is also used in rotating shopwindow displays to make them turn slowly. Pairs of gears the same size change the direction of turning without changing the speed.

Gear wheels at right angles (bevel gears) to each other can change vertical motion into horizontal motion. Hand-operated eggbeaters and drills use this arrangement. An idler gear can be used between the driving and driven gears to make them turn the same direction. Rack and pinion gears consist of a flat row of teeth called a rack and a circular gear wheel. A corkscrew changes circular movement of the driving gear into the upward straight line movement that pulls the cork out.

Why do we use gears?

We use gears to make our work easier. Sometimes we need gears as a force multiplier (eg. hand drill) and sometimes we need them as a speed multiplier (eg. egg beater). If the number of teeth on the driving gear is larger than the number of teeth on the driven gear, then it multiplies the speed and visa versa.

Gears at work

• cork screw [using the idea of the rack and pinion]
• eggbeater [using the idea of the bevel gear]
• bicycle pedals and chains

• clocks

Levers

We can also use levers as a type of machine that can help us move objects more easily. There are three types of levers that you can construct. A first order lever in which the fulcrum or pivet point is in the middle and the load and effort are on opposite sides of the fulcrum. A second order lever in which the effort and load are on the same side but the effort is further away from the fulcrum. A third order lever in which the effort and load are on the same side but the load is further away from the fulcrum. A machine is any device that can be used to overcome a force called a load.

First order lever system	Second order lever system	Third order lever system
Beam balance, old fashioned shop balances, using a hammer to remove a nail, a removalist's hand trolley, pliers, scissors...	Wheel barrow, bottle opener, nutcracker...	Hammering a nail, fishing rod, tweezers ...,

Pulleys

We can also use pulleys to help us move heavy objects. The ratio of the number of ropes that need to shorten compared to the effort rope tells you and what speed it is slowed down by and also the force multiplier it helps you with. Here are two examples ...

Single Pulley System	Double Pulley System	Triple Pulley System
The amount of effort equals the amount of load. The distance you pull the effort rope is the same distance the load rope will move.	The amount of effort equals half the amount of load but the distance you pull the effort rope is twice the distance the load rope will move.	The amount of effort equals a third of the amount of load but the distance you pull the effort rope is three times the distance the load rope will move.