Greco 6th: Machines
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23 terms
Terms | Definitions |
|---|---|
 Define work. | Work means using force (pushing or pulling) in order to move an object a certain distance. |
| Work Formula: | Work = force x distance W = f x d |
| Mr. Moore pushes a box with a force of 500 Newtons over a distance of 2 meters. How much work was done? | The force is 500 Newtons and the distance is 2 meters and we are looking for how much work was done. Therefore: W = f x d W = 500 N x 2 m W = 1000 N/m W = 1000 Joules |
| What is a machine? | A machine is any device that helps make work easier. |
| What is the difference between a simple and a compound machine? | A simple machine is a tool made of one or two parts and a compound machine contains two or more simple machines. |
| Identify the following as a simple or a compound machine: car, nail clippers, airplane, chopsticks | car = compound machine nail clippers = simple machine airplane = compound machine chopsticks = simple machine |
| A lever is made of... | one or more bars resting on a support. The support is called the fulcrum. Levers apply an effort force to a load. |
| Levers can change the... | amount of force or the direction of the force. |
| Difference between the 3 classes of levers: | The difference between the 3 classes of levers is the location of the effort force, fulcrum, and load. |
| Some examples of levers: | Seesaw and pliers are first class levers. Nutcracker and wheelbarrow are 2nd class levers. Chopsticks and a crab's claw are 3rd class levers. |
| An inclined plane is a... | straight slanted surface. A example is a ramp. |
| Why are inclined planes helpful? | An inclined plane or ramp makes moving a load from a low place to a higher place easier. Moving the load up a ramp takes less force than lifting it straight up but the load travels a greater distance. In both cases, you do the same amount of work. |
| A wedge is... | one or two inclined planes that move. The slanted edges of the inclined planes come to a point. |
| How does a wedge do work? | To do it work, a wedge must be moving like a knife or ax. A force directed at the flat end of the wedge drives the point forward. The inclined planes of the wedge change the direction of the force. |
| What is a screw? | A screw is an inclined plane wrapped in a spiral around a cylinder. The ridges of the screw are called threads. If you could unwind the threads, you would see they form an inclined plane. |
| Why are screws important simple machines? | When turned, a small force is applied over a long distance along the inclined plane. The screw applies large force through a short distance when it is pushed. Screws are often used as fasteners. Examples are jar lids and light bulbs. |
| What is a wheel and axle? | It is a wheel with a rod that goes through the wheel's center. The diameter of the wheel is much larger than the diameter of the axle. Examples are water faucets, ferris wheels, and door knobs. |
| How does a wheel and axle work? | The wheel turns through a much greater distance than the axle. But the smaller turn of the axle is much more powerful. A wheel and axle can increase a force or increase the distance through which a force acts. |
| What is a pulley? | A pulley is a grooved wheel with a rope, chain, or belt around it. A load is attached to one end of the rope and the effort force is applied to the other end. |
| What is the difference between a fixed and a movable pulley? | A fixed pulley doesn't move, it changes the direction of the force. A movable pulley moves with the object. Movable pulleys decrease the amount of force you must apply, but the force you apply occurs over a greater distance. |
| How does a flagpole work? | A flagpole is a fixed pulley. There is no change in force however, there is a change in direction because as you pull a flag pole rope down the flag goes up. |
| What is a block and tackle? | A block and tackle uses a fixed pulley and a movable pulley together. A block and tackle with a lot of pulleys could help lift a very heavy load, like a piano. |
| Does using a machine change how much work is done? | No, the amount of work is the same however, the amount of force or distance changes. |
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