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Transcript of Levers
What are levers?
Sometimes a heavy object (load) is too heavy for humans to lift, so the force needed to lift this load (effort) is decreased by adding a lever, resting on a fulcrum (pivot). An example of this is a spanner. Its long handle lets you undo a nut that would be impossible to undo with your hands. The handle provides distance between the force you apply and the load, making the effort needed less.
All levers are one of three types, called classes. The class of a lever depends on the position of the load, effort and fulcrum:
A class 1 lever has the load and the effort on opposite sides of the fulcrum, like a seesaw. Examples of a class-one lever are a pair of pliers and a crowbar.
A class 2 lever has the load and the effort on the same side of the fulcrum, with the load nearer the fulcrum. Examples of a class-two lever is a wheelbarrow.
A class 3 lever does not have the mechanical advantage of class-one levers and class-two levers, because the effort and the load are both on the same side of the fulcrum, but the effort is closer to the fulcrum than the load, so more force is put in the effort than is applied to the load.
The fulcrum (or pivot) is the point where the load is pivoted.
The effort is the force applied to move the load.
The load is the object you are trying to move.
Mechanical Advantage & Velocity ratio
Class 1 and class 2 levers both provide mechanical advantage. This means that they allow you to move a large output load with a small effort. Mechanical advantage is calculated like this:
Mechanical advantage = load/effort
However, to make the effort smaller, the distance you have to travel increases. This is calculated by the velocity ratio:
Velocity ratio = distance moved by effort/distance moved by load