Levers
A A simple machine consisting of a pivot, effort and load. consists of:
- a A point around which something can rotate or turn.
- an Force used to move a load over a distance.
- a The overall force that is exerted, usually by a mass or object, on a surface.
The table shows some examples of the different types of lever:
| Arrangement of compoents | Examples |
| effort - pivot - load | see-saw, crowbar, scissors |
| pivot - load - effort | wheelbarrow, nutcracker |
| pivot - effort - load | tweezers, cooking tongs |
| Arrangement of compoents | effort - pivot - load |
|---|---|
| Examples | see-saw, crowbar, scissors |
| Arrangement of compoents | pivot - load - effort |
|---|---|
| Examples | wheelbarrow, nutcracker |
| Arrangement of compoents | pivot - effort - load |
|---|---|
| Examples | tweezers, cooking tongs |
Simple levers and rotation
A simple lever could be a solid beam laid across a pivot. As effort is applied to rotate one end about the pivot. The opposite end is also rotated about the pivot in the same direction. This has the effect of rotating or lifting the load.
Levers, such as this one, make use of moments to act as a Something that increases the effect of a force.. They allow a larger force to act upon the load than is supplied by the effort, so it is easier to move large or heavy objects.
Example
A solid beam 0.5 m long is laid across a pivot to form a simple lever. The pivot is 0.1 m from the end of the beam. Calculate the heaviest load that could be lifted using a force of 500 N.
First, calculate the moment due to the 500 N force. To do this, distance will also need to be calculated. To lift the greatest load, the effort must be applied furthest from the pivot.
Calculate the greatest distance from the pivot:
0.5 鈭 0.1 = 0.4
Then use the values to calculate the moment:
\(M = F~d\)
\(M = 500 \times 0.4\)
\(M = 200~Nm\)
Second, use the answer above to calculate the maximum force 0.1 m from the pivot.
Rearrange \(M = F \: d\) to find F:
\(F = \frac{M}{d}\)
\(F = 200 \div 0.1\)
\(F = 2000~N\)
The heaviest load that could be lifted by this arrangement is 2,000 N. The lever has the effect of multiplying the force by 4 times - it is a 4脳 force multiplier.