The lever is the simplest mechanism known to our ancestors from time immemorial, it represents the solid body rotating around a motionless point-to-point of a support. The lever serves for receiving a prize in force, for commission of work or for change of the direction of application of force. The usual stick, scrap, a board can act as the lever. A kind of the lever are also the collar and the block. And ways of search of a point of support depending on it can be various.
It is required to you
- - lever;
- - cargoes;
- - dynamometer;
- - ruler.
Instruction
1. The vector of force of F applied to the lever lies on a straight line which is called the line of action of force. The shortest distance from this line to a point of support – a shoulder of strength of L. The lever is in balance provided that the relation of forces applied to it in inverse proportion to the relation of shoulders of these forces: F1/F2=L2/L1 (formula 1). Thus, the point of support can be found if forces of F1 (loading), F2 (ongoing effort) and length of the lever L are known.
2. By means of a dynamometer measure the size of forces of F1 and F2 in newtons. Measure by a ruler length of lever L and write down value in meters.
3. Finding of a point of support for the lever of 1 sort. Such lever is called still by "Yoke" or "Scales". Lines of action of forces are on different sides from an axis of rotation of the lever. A swing, scissors, pincers will be an example of such lever. In this case L=L1+L2. Express length of one of lever shoulders through length of other shoulder and length of all lever: L2=L-L1 (formula 2).
4. Substitute formula 2 in formula 1: F1/F2=(L-L1)/L1 (formula 3). From formula 3 by transformations express L1: L1=F2*L / (F1+F2) (formula 4). Substitute the corresponding F1, F2 and L values in formula 4 and calculate L1 value. From a point of application of force of F1 postpone the received length of L1 and make a notch. It will also be a required point of support of the lever of 1 sort.
5. Finding of a point of support for the lever 2 sorts. Such lever carries the name "Wheelbarrow". In this case forces work on one side from a point of support, and the effort of F2 appears on the free end of the lever. By such principle nippers for splitting of nuts, wheelbarrows work. In this case a point of support is that end of the lever which is closer to a point of application of loading, F1 forces.
6. Finding of a point of support for the lever 3 sorts. Such lever is called "Tweezers". Here forces work on one side from a point of support too, as well as in the lever 2 sorts. But the effort of F2 is made between an axis of rotation of the lever and loading of F1. Such scheme is used during the work of a human forearm, tweezers. In this case the point of support is the end of the lever opposite to loading.