![]() ![]() An example of the force being applied to the axle is on a Ferris Wheel: the wheel spins because of the force on the axle. The example of an old well is a case of the force turning the wheel. It slides along a rope, rather then a rope sliding along it.Ī block and tackle is a combination of fixed and moveable pulleys, and is used to both change the direction and the amount of the force needed to do work.Īn example of a wheel and axle is an old-fashioned well, where a wheel is turned in order to crank the connected axle around, and the rope that the water pail is attached to then wraps around the axle.Ī wheel turns because of effort force and resistance pushing against it the force can be exerted on either the axle, or the wheel. Since it is easier to pull down using your own weight than to pull upwards, fixed pulleys are commonly used.Ī moveable pulley is attached to a load and is used to reduce the amount of force needed to do work. Pulleys are modified levers their fulcrum is at their center.Ī fixed pulley is used to change the direction of force needed to do work in order to hoist up a load with a pulley and rope, force is exerted downward on the rope. An example of a lever is a bottle-opener: the handle acts as a lever arm, and the pivot that fits under the rim of the cap acts as a fulcrum.Ī pulley is a wheel with a grooved rim that is used to reduce the amount of force and change the direction of force needed to do work. Levers raise and lower an object as force is exerted upon the lever. Levers are a bar or board that turn on a fixed support called a fulcrum. Discuss with them which screws are easiest to turn, and explain how the number of threads and the diameter of the screw affects this. You might want to allow your children to experiment by driving different types of screws into a board. The more “threads” (twists) on a screw, the less force required to drive it into something. Screws are basically an inclined plane wrapped around a middle section. Its sides slant down to a point, so that it can be driven into an object by an effort force. A ramp is an example of an inclined plane.Ī wedge is shaped like two inclined planes placed back to back. Since the force needed to push an object up an inclined plane is less than the force needed to lift the same object, inclined planes reduce the amount of force necessary to do a job. ![]() Wedges and screws are both a type of inclined plane pulleys and wheels and axles are both a form of lever.Īn inclined plane is a board or other flat surface set at an angle to the horizontal. There are six types of simple machines: pulleys, wheels and axles, inclined planes, levers, wedges, and screws. Simple machines cannot change the amount of work done, but they can reduce the effort force that is required to do the work!Īs you can see by this formula, if the effort force is reduced, distance is increased. The scientific formula for work is w = f x d, or, work is equal to force multiplied by distance. Simple machines make work easier by multiplying, reducing, or changing the direction of a force. Simple Machines Science Lesson Introduction to Simple Machines That is the beauty of levers – making work easier by lowering the amount of force that is required to lift or move something! When the fulcrum was in the middle of the lever, the effort force had to be greater than the load force in order to lift the load force up.īut, by simply changing the pivot point of the lever, we were able to use a smaller effort force to lift the greater load force. The lighter weight we used to lift the load force is called the effort force. ![]() In our experiment above, the heavy object we were trying to lift is called the load force. When talking about levers, things can get a little confusing, so there are a few terms we can use to help keep things straight. What do you think would happen if you moved the fulcrum the opposite direction? It would take more force, or in this example, a heavier weight to lift the object! Moving the fulcrum closer to the object made it much easier to lift a heavy object. Moving the lever’s pivot point closer to the object you were trying to lift changed how much force (or work) it took to lift the object. This didn’t change anything about the lighter weight – it stayed exactly the same. With the heavier object on one end, the lighter (empty) end of the lever was raised up.īy moving the fulcrum closer to the heavy end, you were able to use the lever to help you raise the heavier object when you placed a lighter one on the opposite end. To understand how a lever works – picture a playground see-saw. In this experiment, you took a basic ruler or piece of wood and added a fulcrum to make a simple machine called a lever! You can experiment more by moving the fulcrum and changing the placement of the weights. ![]()
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