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Post on 11-Nov-2014
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DESCRIPTIONYear 6 - Sc Note
- 1. Machine is any device or tool used to make work easier Simple machine is a simple tool used to make the work easier. Examples : wheel and axle, lever, wedge, pulley, gear, inclined plane and screw. Complex or compound machine has more than two simple machine working together. Examples : bicycles, electric blenders and wheelbarrows
- 2. It consists of a larger wheel that is connected to a smaller rod called axle. They are connected in such way that they rotate together. A wheel and axle is a force magnifier. A small force applied to the wheel provides a larger force at the axle. Wheel and axle are used in many devices for example screwdriver, roller skate, cross-spanner and water tap.
- 3. A lever is a rod that rests and turns about a fixed point. A fixed point is called the fulcrum. Force is applied at some point of the rod. This force is called the effort. Applying a force to one end of the rigid object causes it to pivot about the fulcrum, causing a magnification of the force at another point along the rigid object. There are three classes of levers, depending on where the input force, output force, and fulcrum are in relation to each other. Baseball bats, seesaws, wheelbarrows, and crowbars are types of levers.
- 4. Examples: Seesaw (also known as a teeter-totter) Crowbar Pliers (double lever) Scissors (double lever)
- 5. Examples: Wheelbarrow Nutcracker (double lever) The handle of a pair of nail clippers
- 6. Examples: Human arm Tongs (double lever) (where hinged at one end, the style with a central pivot is first-class) Catapult Any number of tools, such as a hoe or scythe The main body of a pair of nail clippers, in which the handle exerts the incoming force
- 7. An inclined plane is a plane surface set at an angle to another surface. This results in doing the same amount of work by applying the force over a longer distance. The most basic inclined plane is a ramp; it requires less force to move up a ramp to a higher elevation than to climb to that height vertically. The wedge is often considered a specific type of inclined plane.
- 8. A wedge is a simple machine used to separate two objects, or portions of objects, through the application of force. A wedge is made up of two inclined planes. These planes meet and form a sharp edge. This edge can split things apart. Wedges are used as either separating or holding devices. There are two major differences between inclined planes and wedges. First, in use, an inclined plane remains stationary while the wedge moves. Second, the effort force is applied parallel to the slope of an inclined plane, while the effort force is applied to the vertical edge (height) of the wedge.
- 9. Wedges are used as either separating or holding devices. A wedge can either be composed of one or two inclined planes. A double wedge can be thought of as two inclined planes joined together with their sloping surfaces outward. Examples of wedges are: knives, axes, forks and nails The common "door wedge" uses the force on the surfaces to provide friction, rather than separate things, but its still fundamentally a wedge.
- 10. A pulley is a wheel with a groove along its edge, where a rope or cable can be placed. It uses the principle of applying force over a longer distance, and also the tension in the rope or cable, to reduce the magnitude of the necessary force. Complex systems of pulleys can be used to greatly reduce the force that must be applied initially to move an object.
- 11. Pulleys are used to lift up or lower down objects. Pulleys make our work easier by:1. Changing the direction of a force2. Lift a load with less effort. The more pulleys use the lesser the effort is needed.
- 12. Gears have many uses in our lives. They are used to : - multiply or reduce speed and force; - change the direction of motion - transmit a force over a distance Examples : watch, egg beater, hand drill and gear in a bicycle In a gear train we have a gear known as the driver and one known as the follower. Driver - is the gear that has the force or motion input. Follower - is the gear that results in the force or motion output.
- 13. The gear ratio of a gear train is the number of teeth on the follower divided by the number of teeth on the driver. In the gear train above the driver has 18 teeth while the follower has 8 teeth. Therefore the gear ratio is 8/18 or 4/9. For every 4 turns of the driver the follower turns 9 times. This gear train can be used to multiply speed on a bicycle if the follower was connected to a wheel and the driver connected to the paddles.
- 14. Low gear ratio = more speed = less force High gear ratio= less speed = more force
- 15. A screw is a simple machine that is made from another simple machine. It is actually an inclined plane that winds around itself. A screw has ridges and is not smooth like a nail. Some screws are used to lower and raise things. They are also used to hold objects together. Screw can be used to fasten or hold things tightly together or to raise weight Examples : corkscrew, screw cap bottle, jackscrew, g damp
- 16. Also known as compound machine. Consist of two or more simple machines. For example: Scissors is actually combination of a wedge and a lever Watch is combination of gears and wheel and axle Hand drill is combination of gear, wedge, wheel and axle Wheelbarrow is combination of lever and wheel and axle Bicycle is combination of levers, wheel and axle, gears and screws
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