Simple Machines Work Mechanical Advantage and Efficiency Simple

Simple Machines Work, Mechanical Advantage and Efficiency

Simple Machines § All machines can be classified as or a combination of levers and inclined planes. § Manipulates the Law of Conservation of Energy § The amount of energy that goes in the machine = to the amount of energy that comes out. § Work in = Work out § Fin x d in = F out x d out

Machines and Work § Machines DO NOT decrease work!!! § They change the Force and distance needed to get a certain amount of work done. F d F d

Work Done F in x d in = F out x d out Fin x 1. 75 m = 2000 N x 0. 25 m Fin = 2000 N x 0. 25 m Fout 1. 75 m 2000 N d in= 1. 75 m Fulcrum/ Pivot point d out= 0. 25 m Fin = 286 N

Mechanical Advantage § How much a machine changes the force § There are 4 variables § Fe = “effort force”: how much YOU put in. § Fr = “resistance force”: force generated by machine. § de = “distance effort”: distance effort must travel i. e. length of a lever’s effort arm. § dr = “distance resistance”: distance the resistance must travel i. e. the length of the resistance arm in a lever.

Mechanical Advantage Fr Fe de Fulcrum/ Pivot point dr

Ideal Mechanical Advantage § Model of a machine in an “ideal” world. § No friction or heat loss. § Ideal mechanical advantage = distance effort/distance resistance. § IMA = de/dr § This is a ratio so there are no units

Mechanical Advantage §In the “real” world energy is lost as friction and heat. §Mechanical Advantage = resistance force/effort force §MA = Fr/Fe §No units

Efficiency §Workout / Workin x 100 §The ratio of a machine’s MA to its IMA determines its efficiency. §Efficiency = MA / IMA x 100.

Levers § 3 lever types § Class 1 lever: § Ex: crowbar § Label § § Fe Fr de dr Fulcrum/ Pivot point Fe = “effort force” Fr = “resistance force” de = “distance effort” dr = “distance resistance”

Levers § Class 2 lever: § Ex: wheel barrow § Label Fr § § Fe = “effort force” Fr = “resistance force” de = “distance effort” dr = “distance resistance” dr Fulcrum/ Pivot point de Fe

Levers § Label § § Class 3 lever: § Ex: bicep Fr de Fulcrum/ Pivot point Fe = “effort force” Fr = “resistance force” de = “distance effort” dr = “distance resistance” Fe dr

Inclined Plane § Example: ramp dr Fr de Fe

More simple machines § Wedge: Inclined plane § Screw: Inclined plane wrapped around a cylinder Lever § Wheel and axle: § Pulley: Variation of wheel and axle

Height does not change, only the angle. Height = 0. 5 m

Scale reads = 300 g Car mass = 500 g Height = 0. 5 m Length = 0. 83 m 300

Modified test Scale reads = 3 N Car mass = 5 N Height = 0. 5 m Length = 0. 83 m 300

Scale reads = 300 g Car mass = 400 g Height = 0. 5 m Length = 0. 66 m 300

Inclined Plane Distance Force Distance • Example: ramp dr Fr de Fe

Mechanical Advantage Example 200 N Fe Fr 1 m 4 m dr de 75 N

500 N

Class 1 lever Class 2 lever Fr Fe dr de Fe Fr de dr Fr dr Class 3 lever Fe Fe de de Fr dr

Force Resistance Fulcrum