Work, Power, & Machines What is work Is work being done or not Do you do more work when you finish a job quickly The Joule
LaRue, Stephanie, Features Editor has reference to this Academic Journal, PHwiki organized this Journal Work, Power, & Machines What is work The product of the as long as ce applied to an object in addition to the distance through which that as long as ce is applied. Work = Force (N) x Distance (m) 1 Nm = Joule (J) Is work being done or not Mowing the lawn Weight-lifting Moving furniture up a flight of stairs Pushing against a locked door Swinging a golf club YES YES YES NO YES
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Do you do more work when you finish a job quickly Work does NOT involve time, only as long as ce in addition to distance. No work is done when you st in addition to in place holding an object. Would you do more work if you ran up the stairs in addition to skipped 2 at a time The Joule 1 newton-meter is a quantity known as a joule (J). Named after British physicist James Prescott Joule. How quickly work is done. Amount of work done per unit time. If two people mow two lawns of equal size in addition to one does the job in half the time, who did more work Same work. Different power exerted. POWER = WORK / TIME
The watt A unit named after Scottish inventor James Watt. Invented the steam engine. P = W/t Joules/second 1 watt = 1 J/s watts Used to measure power of light bulbs in addition to small appliances An electric bill is measured in kW/hrs. 1 kilowatt = 1000 W Horsepower (hp) = 745.5 watts Traditionally associated with engines. (car,motorcycle,lawn-mower) The term horsepower was developed to quantify power. A strong horse could move a 750 N object one meter in one second. 750 N
Machines A device that makes work easier. A machine can change the size, the direction, or the distance over which a as long as ce acts. Forces involved: Input Force FI Force applied to a machine Output Force FO Force applied by a machine Two as long as ces, thus two types of work Work Input work done on a machine =Input as long as ce x the distance through which that as long as ce acts (input distance) Work Output Work done by a machine =Output as long as ce x the distance through which the resistance moves (output distance)
Can you get more work out than you put in Work output can never be greater than work input. Mechanical Advantage (MA) expressed in a ratio WITH NO UNITS!! The number of times a machine multiplies the input as long as ce. 2 types of mechanical advantage IDEAL Involves no friction. Is calculated differently as long as different machines Usually input distance/output distance ACTUAL Involves friction. Calculated the same as long as all machines
Different mechanical advantages: MA equal to one. (output as long as ce = input as long as ce) Change the direction of the applied as long as ce only. Mechanical advantage less than one An increase in the distance an object is moved (do) Efficiency Efficiency can never be greater than 100 %. Why Some work is always needed to overcome friction. A percentage comparison of work output to work input. work output (WO) / work input (WI) Simple Machines 6 different types of simple machines: 1.) the lever 2.) the wheel in addition to axle 3.) the inclined plane 4.) the wedge 5.) the screw 6.) the pulley
1. The Lever A bar that is free to pivot, or move about a fixed point when an input as long as ce is applied. Fulcrum = the pivot point of a lever. There are three classes of levers based on the positioning of the ef as long as t as long as ce, resistance as long as ce, in addition to fulcrum. INPUT FORCE (EFFORT FORCE) OUTPUT FORCE (Resistance Force) INPUT ARM (EFFORT DISTANCE) OUTPUT ARM (RESISTANCE DISTANCE) FULCRUM First-Class Lever The position of the fulcrum identifies a first-class lever. The fulcrum of a first-class lever is ALWAYS located between the input as long as ce (ef as long as t) in addition to the output as long as ce (resistance) Depending on position of fulcrum, MA of first-class lever can be greater than 1, equal to 1, or less than 1
Which ones are first-class levers Second-Class Levers Output as long as ce is located BETWEEN the input as long as ce in addition to the fulcrum Example of second-class lever When you lift h in addition to les of wheelbarrow, it rotates around its fulcrum Input distance greater than output distance Increased input distance means it takes LESS as long as ce from you to lift the load MA of a second-class lever is always greater than 1
Third-Class Levers Input as long as ce is located between the fulcrum in addition to the output as long as ce The output distance over which the lever exerts its as long as ce is always larger than the input distance you move the lever through. There as long as e MA as long as third-class levers is always less than 1 Wheel & Axle Consists of 2 discs or cylinders, each one with a different radius. wheel axle Can have MA greater than or less than 1 Would the MA as long as the steering wheel be greater than or less than 1 Greater than 1: input distance larger than output distance Inclined Planes Imagine how hard it would be to walk up the side of a steep hill. It would be MUCH easier to follow a gentle slope of a winding trail .why is this What is happening to input distance if you decide to take the curvy trail instead of going straight up the hill Because input distance is greater than output distance, in this case, the input as long as ce is decreased so its easier as long as you!
Inclined Planes Inclined plane: a slanted surface along which a as long as ce moves an object to a different elevation Input distance Output distance Inclined Planes What is the MA of the following inclined plane 6m 1 m Mechanical Advantage = 6 MA as long as inclined plane will NEVER be less than 1 Wedges & Screws Similar to inclined planes BUT sloping surfaces can move. Wedge: a V-shaped object whose sides are two inclined planes sloped toward each other. A thin wedge of a given length has a greater MA than thick wedge of the same length. Why is this so Length of wedge is divided by width of the opening. Smaller the opening (thickness), the larger your MA will be Examples: knife, axe, razor blade
MA = Count of ropes that apply an upward as long as ce (note the block in addition to tackle!) Fe A combination of two or more simple machines. Cannot get more work out of a compound machine than is put in.
LaRue, Stephanie Features Editor
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