Moments, Levers and gears.

A moment is a turning force. A turning force is when force is applied that causes the object to rotate. Coincidently this is how you find the centre of mass when in a zero gravity environment. A moment can be defined by the equation, moment (Newton meters) = force (Newton's) x perpendicular distance (Meters). Perpendicular distance is the length of space directly across from the pivot to when the force is applied. When forces are in equilibrium (At equals) the moment in the anticlockwise direction is equal to the moment in the clockwise direction.

Key Terms
Centre of mass = The point in an object when all mass seems to act towards.
Driver gear = The cog that is motor assisted.
Driven gear = The cog that is moved via another cog.
Equilibrium = where things cancel each other out, forces in equilibrium are forces that act against each other so there is no resultant force.
Force multiplier = something that takes a small force and makes it larger.
Gear Ratio = number of teeth on the driven gear / number of teeth on the driver gear
Moment = the turning force about a fixed point.
Perpendicular distance = the distance from the pivot, that takes into account only the distance in one direction, either horizontally or vertically.
Pivot = a fixed point.
Teeth = sticking out parts in a cog.
Turning force = a farce that causes an object to rotate.
Driver gear = The cog that is motor assisted.
Driven gear = The cog that is moved via another cog.
Equilibrium = where things cancel each other out, forces in equilibrium are forces that act against each other so there is no resultant force.
Force multiplier = something that takes a small force and makes it larger.
Gear Ratio = number of teeth on the driven gear / number of teeth on the driver gear
Moment = the turning force about a fixed point.
Perpendicular distance = the distance from the pivot, that takes into account only the distance in one direction, either horizontally or vertically.
Pivot = a fixed point.
Teeth = sticking out parts in a cog.
Turning force = a farce that causes an object to rotate.
Turning forces
The turning force is pretty self explanatory , it is a force that causes something to rotate/turn. When a turning force is applied to something about a pivot this is known as a moment. Think of this in terms of a door in your house or school. When you push or pull on the door you are applying force. When this force is applied the door turns so that you can pass through it.

Levers
Levers are amazing things that have helped achieve some of the largest engineering projects across the world. For example when the tower bridge lifts it uses moments to balance out the force so that boats can pass through. A lever essentially is used to decrease the amount of force inputted for the resultant force still to occur, this is known as a force multiplier. But how does it work? If we take the moment equation (Moment= force x perpendicular distance), to keep the moment the same as one increases the other must decrease. Meaning that if you increase the perpendicular distance then the force applied must decrease if the moment is to stay the same. Archimedes is known to have once said "give me a lever and a fulcrum in which to place it then I will move the world"

Gears
Much like a lever, a gear is a force multiplier. A gear works by two cogs working together, the driver gear which is the one where the motor is attached and the driven gear which is the one that is pushed by another gear. Unlike wheels, each gear has bits that stick out known as teeth. These "Bite" together in order to cause each other to move. For a gear to increase the force the driven gear needs to have more teeth (be bigger) than the driver gear. To explain this we need two equations,
1. Gear Ratio = Number of teeth in the driven gear / number of teeth on the driver gear. 2. Output speed = Input speed / Gear ratio. To put this into perspective, if the original driven gear has 10 teeth and the original driver gear has 5 teeth the ratio is 2. Where as if you change this so that the driver gear has 10 teeth then the gear ratio will be 1, making equation 2 output speed = input speed as the number of teeth in each cog is equal. 
Related Resources
This topic is covered by the Code Ph.10. and there are resources available in the THS store for this topic. Student worksheets are free and we have a range of quality lessons available for purchase, these include lesson plans, activity's and presentations for each lesson.

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Check the Spec'
The specifications we have used for this page are:
AQA (Spec 8463) 4.5.4 Moments, Levers and gears.
OCR (Gateway science 2016 GCSE 91 Physics A) P2.3I – P2.3o
AQA (Spec 8463) 4.5.4 Moments, Levers and gears.
OCR (Gateway science 2016 GCSE 91 Physics A) P2.3I – P2.3o