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Work
Power
Simple Machines
Energy
Work
Work is done on an object when the object moves in the
same direction in which the force is exerted.
Formula: Work = Force x Distance
Units:
Work is measured in Joules (J)
Force is measured in Newtons (N)
Distance is measured in meters (m)
Power
 Power is the rate of transfer of energy or the rate at
which work gets done.
 Power = Work / Time
 Power = Watts (W)
 Work = Joule (J)
 Time = seconds (s)
Pulley
 A pulley is a simple machine made of a grooved wheel
with a rope or cable wrapped around it.
Types of Pulleys
 Single Fixed Pulley:
attached to the structure, like
a flag pole
 Does not change the amount
of force applied
 Does change direction of the
force
Types of Pulleys
 Single Movable Pulley:
this pulley is attached to
an object you wish to
move
 Decreases the amount of
input force needed
 Does not change the
direction of the force.
Types of Pulleys
 Block and Tackle:
combination of fixed
and moveable pulleys
 Decreases input force
even more than a
moveable pulley
Mechanical Advantage
 MA = Output force / Input force
MA also equals the number of sections of rope
that support the pulley
Inclined Plane
 An inclined plane is a flat, sloped surface.
An inclined plane allows you to exert your input force over a longer distance
Ideal Mechanical Advantage
MA = Length of the incline divided by the height of
incline .
the
Levers
 A lever is a rigid bar that is free to pivot, or rotate, at a
fixed point
 The fixed points that a lever pivots on is called a fulcrum
Ideal Mechanical Advantage
 MA = Distance from fulcrum to input force ÷ Distance
from fulcrum to output force
Input Force
Output Force
Types of Levers
 Levers are classified according to the location of the
fulcrum relative to the input and output forces
1st Class
2nd Class
3rd Class
Examples of Levers
Third Class
Three Other Simple Machines
 Wheel and Axle – a machine consisting of a wheel that turns an
axle so that the two parts rotate together.
 Wedge – a machine with at least one slanting side ending in a
sharp edge.
 Screw – a machine that contains an inclined plane wrapped
around a post.
Compound Machines
 A machine that is made of two or more simple
machines.
Energy
 Energy is the ability to do work or cause change.
Kinetic energy is the energy an object has due to its motion. Formula: KE = ½ mv2
Ex: a ball dropped off of a ledge, a bike going up a hill and down a hill
Potential energy is stored energy that results from the position or shape of an object.
Ex: holding a ball at the top of a ledge, a bike at the top of the hill
Gravitational Potential Energy
 (GPE) is the energy related to an objects height. The
higher an object is raised the more GPE.
 Formula: GPE = Weight (N) x Height (m)
Elastic Potential Energy
 Elastic potential energy is the energy associated with
objects that can be stretched or compressed.
Conservation of Energy
 According to the Law of Conservation of Energy, energy cannot be
created or destroyed it changes forms.
 Example: In a pendulum system, energy changes occur between
potential and kinetic energy.
 Most forms of energy can be transformed into other forms.
 Example: A toaster transforms electrical energy into thermal
energy.