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What is a ramp? A ramp (inclined plane), helps us to move heavy objects more easily, but we have to move them further to complete the task. We use less force; however, we have to apply the force over a greater distance. Friction is one problem encountered in using a ramp to move heavy objects. What is a wedge? A wedge consists of two back-to-back inclined planes. A wedge looks like an inclined plane but it works differently. It can either hold things together, as in a doorstop or nail, or it can split things apart, as in an axe or chisel. Other wedges include the cutting edge of scissors, knives and screwdrivers. What is a screw? A screw is an inclined plane wound about a nail. The ridges are called the thread of a screw. These threads cut a groove in the wood as you turn the screw, making it hold very tightly. To remove a screw you have to turn in the opposite direction with a screwdriver. It is very difficult to remove a screw by pulling it straight out. The distance between the threads depends on the slope of the inclined plane - the steeper the slope, the wider the thread. Screws with less distance between the threads are easier to turn. What is a lever? The lever is a bar that turns on a point called a fulcrum. The secret of the lever is the increased distance over which the force moves, i.e., the arm length of the lever, which is determined by the position of the fulcrum (pivot). It is the same principle as the inclined plane - the greater the distance over which the force must be applied, the smaller the force required to do the work (lift the load). A shovel, wheelbarrow, hockey stick, wooden bat and tweezers are also levers. From: http://science.jrank.org/pages/4060/Machines-Simple.html |
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