MachinesReview and summary of important topics

Table of Contents Work, Power & Force Simple Machines Types of Simple Machines Compound Machines Mechanical Advantage Efficiency

Work, Power & Force Work: Transfer of energy from one

object to another by force Measured in JOULES W = F x d

Power: Rate at which work is done Measured in WATTS P = W/t

Simple Machines A simple machine does work using only

one movement

What are the 3 ways in which machines can help you do work? Change the distance at which the force is

applied Change the direction of the force Change the size of the force

Types of Simple Machines Inclined Plane Screw Wedge Pulley Wheel & Axle Levers

Inclined Plane A flat, sloped surface

ie: slide, ramp, stairs

Screw An inclined plane wrapped around a

cylinder

Wedge A sloped surface that moves

Pulley A grooved wheel with a rope/wire

wrapped around it

The wheel is attached to a fixed, unmovable surface

The wheel is attached to the object being lifted/moved

Fixed Pulley

Movable Pulley

Wheel & Axle An axle (rod) attached to the center of a

wheel

Classes of Levers 1st Class: Fulcrum is between the input

and output force 2nd Class: Output force is between the

input force and fulcrum 3rd Class: Input force is between the

output force and fulcrum

Ideal Mechanical Advantage of a Lever

Compound Machine 2 or more simple machines combined to

perform a function ie: a gear

Wedges Wheel and axle Lever

Mechanical Advantage Ratio of a machine’s output force to its

input force

No units

MA = Output force/input forceMA = Fout / Fin

Ideal mechanical advantage

IMA – Ideal Mechanical Advantage Ideal mechanical advantage is the

mechanical advantage of a simple machine when friction is not present.

The operation of a machine at its IMA is impossible because friction is always present.

IMA of a Lever = length of input arm length of output arm

Efficiency Ratio of output work to input work

Calculated as a percent ratio

Efficiency = Output work/input work x 100%