Work
In physics, a force is said to do work if, when acting, there is a displacement of the point of application in the direction of the force.
W = F x d (measured in joules, J)
Work transfers energy from one place to another or one form to another. See work energy theorem to the right
Power
In physics, power is the rate of doing work, the amount of energy transferred per unit time. Having no direction, it is a scalar quantity. In the International System of Units, the unit of power is the joule per second (J/s), known as the watt in honor of James Watt, the eighteenth-century developer of the steam engine.
What is a simple machine?
Simple machines make work easier by multiplying, reducing, or changing the direction of a force. The scientific formula for work is w = f x d, or, work is equal to force multiplied by distance. Simple machines cannot change the amount of work done, but they can reduce the effort force that is required to do the work! For the inclined plane and lever, less effort (effort force) is needed to do the same work because the distance is increased. By using simple machines, the Egyptians were able to construct the pyramids.
Terms can be confusing!
As seen in the picture to the right, AMA is calculated by dividing the resistance force by the effort force. In other sources, you will see these labeled as output force and input force respectively. Resistance force is the WEIGHT of the object to be moved. It is the output force of the simple machine. The input force is the same as the effort force put into moving the object using the machine. This formula for AMA is the same for the lever and the inclined plane.
Just as with inclined planes, terms can be confusing with levers too.
As the picture to the left shows, the IMA for a lever can be calculated by taking the length of the lever arm from the fulcrum to the force (effort) divided by the length of the lever arm from the fulcrum to the load. Another way you will see this shown is effort distance/resistance difference. And still another way (as seen below), input arm length/output arm length = IMA. As with inclined planes, the object to be moved is the resistance force or load and the effort is the force put into moving the load at the other end of the fulcrum. So force=effort=in and resistance = load=out.
