| A | B |
|---|
| work formula | work=force times distance(W=F x d) |
| You move a 75 kg refrigerator 35m. this requires a force of 90N. How much work, in joules was done while moving the refigerator? | 3,150N.m = 3,150 J |
| power formula | Power+ work/time (P=W/t) |
| It took 5 minutes to move a plasma TV. You did 3,150 joules of work in the process. How much power was required tom move the TV? | 10.5 W |
| effort force | force applied to the machine |
| resistance force | force applied by the machine to overcome resistance |
| when you try to pull a nail out with a hammer, you apply the effort force to ____? | on the handle |
| the resistance force is where? | the force the claw applies to the nail |
| input work | the work done by you on a machine |
| output work | work done by the machine |
| a measure of how much of the work put into a machine is changed into useful output work by the machine | efficiency |
| the number of times a machine multiplies the effort force | mechanical advantage |
| efficiency formula | Work Output divided by work Input x 100% |
| efficiency of a real machine | always less than 100% because friction causes the output work to always be less than the input work |
| lever | a bar that is free to pivot, or turn about a fixed point |
| fulcrum | fixed point on the lever |
| distance from fulcrum to where the effort force is applied | effort arm |
| the distance from the fulcrum to where the resistance force is applied | resistance arm |
| first class lever | screwdriver; the fulcrum is located between the effort and resistance forces |
| second class lever | wheelbarrow; the resistance force is located between the effort force and the fulcrum |
| third class lever | baseball bat; effort force is located between the resistance force and fulcrum |
| IMA | length of effort arm divided by length of resistance arm |
| pulley | a grooved wheel with a rope or cable running along the groove |
| fixed pulley | IMA is oNE |
| movable pulley | a pulley in which one end of the rope is fixed and the wheel is free to move |
| wheel and axle | consists of two wheels of different sizes that rotate together like a pencil sharpener |
