Download Unit 2 Review Session Part 1

Unit 2 Review Session
Part 1
Work & Simple Machines
What is Work?
• Work is applied energy
• It is equal to the force applied times
the distance over which that force is
applied.
• .
What unit of measurement do we
use for work or energy?
• Work and energy are both measured
using the unit Joule.
• 1 Joule = 1 Newton of force applied over
a distance of 1 meter.
Mechanical Advantage
• Having a mechanical advantage means
the effort needed has been decreased
but the distance over which that effort
must be applied has been increased.
• The amount of work stays the same, its
just easier.
• Mechanical advantage is the ratio of the
output force to the input force.
• MA=Fo / F i
Simple Machines
• Simple machines provide a Mechanical
advantage.
Inclined Plane
• A plane whose angle
to the horizontal is
less than a right angle
• The mechanical
advantage can be
calculated by dividing
the length of the
slope by the height of
the inclined plane.
Wedge
• A Wedge is simply two
inclined planes put
together.
• It is frequently used to
either separate or hold
objects together.
• The Mechanical
advantage is determined
by the length of either
slope divided by the
thickness of the thick
point of the wedge.
The Screw
• The Screw is a modified
inclines plane. It is simply
an inclined plane wrapped
around a central
cylindrical shaft.
• The mechanical advantage
of a Screw is determined
by dividing the
Circumference of the
central shaft by the pitch
of the inclined plane.
Parts of a Lever
• The effort is the
force you put in
(input force).
• The fulcrum is the
pivot point of the
lever.
• The load is what you
are truing to move
(output force).
Levers
• 1st class lever: the
fulcrum is in the middle
between the effort
force and the load. (ex
scissors)
• 2nd class lever: the
fulcrum is at one end the
effort force is at the
opposite end and the
load is in the middle. (ex
door)
Levers continued
• In a 3rd class lever the
fulcrum is at one end
the load at the other
and the effort force
is in the middle. (ex
broom)
Mechanical advantage of a lever
• Mechanical advantage of a lever is the
ratio of the length of the input arm
over the length of the output arm.
• MA= L i / L o
Wheel & Axel
• A wheel and axel is
simply a lever that
has been wrapped all
the way around the
fulcrum which in
tern has been
extended to become
an axel.
The mechanical advantage
of a wheel and axel is the
ratio of the radius of the
wheel to the radius of the
axle.
The Pulley
• A pulley consists of a grooved wheel
that turns freely in a frame called a
block. A pulley can be used to simply
change the direction of a force or to
gain a mechanical advantage, depending
on how the pulley is arranged.
Fixed Pulley
• A pulley is said to be
a fixed pulley if it
does not rise or fall
with the load being
moved. A fixed
pulley changes the
direction of a force;
however, it does not
create a mechanical
advantage.
Moveable Pulley
• A moveable pulley rises
and falls with the load
that is being moved.
• A single moveable pulley
creates a mechanical
advantage; however, it
does not change the
direction of a force.
• The mechanical advantage
of a moveable pulley is
equal to the number of
ropes that support the
moveable pulley
• The illustration, shows two
rope ends support the
moveable pulley.
• Therefore, an effort
force of 50 pounds will lift
a resistance force of 100
pounds.
• The mechanical advantage
is 2.
The rate work is done
is called power.
• Power is work (joules) ÷ time (seconds)
P=W/t
• The Unit for power is watt.
• 1watt = 1 joule/second
The End
of
Part 1
Next Up
Part 2
Review Forms & Transformations
of Energy