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PhysChapter 7
Simple Machines
| Force times Distance (F*D) | work |
| Rate of doing work (W/t) | Power |
| Basic mechanical parts that help us do work | simple machines |
| the force exerted on a simple machine | effort |
| Work out is always __ than work in | less than < |
| a measure of how effectively the work is being used and how much energy is getting converted to other forms that are not being used | efficiency |
| The ___ energy or work produced by a simple machine is always equal to the energy or work put into the machine. Some is just being changed. | total |
| the thing you are moving | load or resistance |
| Resistance Force | F_r |
| the force needed to JUST BEGIN moving the load without the machine | Resistance force |
| the force you actually exert while using the machine | Effort force |
| Effort force | F_e |
| a measure of how the simple machine is multiplying the effort force or motion | Mechanical advantage MA |
| AMA takes into account what? | force or energy lost due to friction |
| Actual mechanical advantage uses what? | forces not lengths |
| simple machines compensate for a smaller effort force by exerting that force over a longer distance | Distance Principle |
| Ideal mechanical advantage uses what? | lengths not forces |
| Effort distance is what? | the distance the load is moved with the machine |
| Resistance distance is what? | the distance the load is moved without the machine |
| a rigid bar that rests on a pivot point called a fulcrum is what? | lever |
| Movement of an object about a central axis or pivot point is what? | Rotational Motion |
| When forces are balanced like on a seesaw when neither side is moving up or down you have what? | Rotational Equilibrium |
| When forces act perpendicularly on a lever rotating around a pivot point it produces this. | A moment or torque |
| Load -- fulcrum --- effort | 1st class lever |
| effort -- load -- fulcrum | 2nd class lever |
| load -- effort -- fulcrum | 3rd class lever |
| examples of 1st class levers | see-saw, skull, foot, pry bar |
| examples of 2nd class levers | hand truck, wheel barrow, paper cutter, door hinge |
| examples of 3rd class levers | arm, leg, fingernail clippers, rakes, broom |
| What does a 1st class lever multiply? | effort force _ makes seem easier to do the work |
| What does a 2nd class lever multiply? | same as 1st class, effort force - so use less force to move the resistance |
| What does a 3rd class lever multiply? | effort motion or distance - resistance moves a lot farther than the effort |
| A modified lever | Wheel and axle |
| modified wheel and axle | gears |
| IMA of gears = | number of teeth on the resistance gear / number of teeth on the effort gear |
| A fixed pulley has an IMA of what? | one |
| A movable pulley has an IMA of what? | two |
| How can you determine the IMA of a pulley system? | Count the pulleys |
| IMA of an inclined plane = | length of the incline (le) / height you lift (lr) |
| A ling thin wedge wrapped around a shaft | screw |
| the number of threads per inch | TPI |
| The greater the pitch on a screw what happens to the mechanical advantage? | it decreases |
| Two or more simple machines working together to make work easier | compound machine |
| examples of a wedge | Axe, knife, zipper |
Created by:
kdcribb
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