Machine Review

Inclined Plane

Effort Force

Load Distance

Load Force

Effort Distance

Pulleys

Effort Distance

LoadDistance

Effort Force

Load Force

Lever

EffortForce

Load Distance

Load Force

Fulcrum

EffortDistance

Classes of Levers

http://www.enchantedlearning.com/physics/machines/Levers.shtml

Simple Machines

Machines help us do work by decreasing the

Effort Force and increasing the Effort

Distance needed to do the work.

Work done remains the SAME! We are lifting

the same load the same distance!

L.F. x L.D. ≈ E.F. x E.D.

Load Force & Load Distance

Load Force: Force a machine exerts to lift a

load. When lifted straight up, it is equal to

the weight of the load.

Load Distance: Distance a load moves when

acted on by a load force.

Effort Force & Effort Distance

Effort Force: Force exerted by a person (or

motor) when using a machine to lift a load.

Effort Distance: The distance over which the

effort force acts in a simple machine.

Mechanical Advantage

Ideal Mechanical Advantage =

Effort Distance / Load Distance

Actual Mechanical Advantage =

Load Force / Effort Force

Mechanical Advantage

A High Actual Mechanical Advantage means:

Little effort force is needed to lift a larger load.

A High Ideal Mechanical Advantage means:

Larger Effort Distance is needed to lift the load

the load distance.

Actual vs. Ideal Mech. Adv.

Actual Mechanical Advantage tends to be

less than Ideal Mechanical Advantage

because of FRICTION!

Input Work and Output Work

Output Work =

Load Force x Load Distance– Define Output Work: Work done on the load by a simple

machine.

Input Work =

Effort Force x Effort Distance– Define Input Work: Work done by the effort force in a

simple machine.

Efficiency

Efficiency =

Output Work/Input Work x 100 A high Efficiency means: amount of output

work is very close to amount of input work. REMEMBER: A machine could have a high

mechanical advantage, but low efficiency – and vice versa.

Equations

Work (N-m) = Force (N) x Distance (m)– Input work = effort force x effort distance– Output work = load force x load distance

Power (W) = Work (N-m) / Time (s) Slope of an Incline = Rise / Run Ideal Mechanical Advantage = Effort Distance / Load

Distance Actual Mechanical Advantage = Load Force / Effort

Force Efficiency = Output Work / Input Work x 100