Transcript Simple Machines PowerPoint

Chapter 5: Work and Machines
 Describe the six types of simple
machines.
 Explain how the different types of
simple machines make work easier.
 Calculate mechanical advantage.
 Simple Machine: a machine that does
work with only one movement of the
machine.
 Lever: a rigid bar that rotates around a
fixed point called the fulcrum.
 The bar may be either independent or
attached to another object.
 In use, a lever has both an input force
and an output force.
Output
Force
Input
Force

First Class Lever: fulcrum is
in the middle of the input
and output forces
 MA may be greater or less
than 1
 Ex: scissors, see-saw,
crowbar
Output
Force
Input
Force

Second Class Lever: output
force is in-between the input
force and the fulcrum.
 MA is always greater than 1
 Ex: wheelbarrow, nut cracker,
bottle opener
Output
Force
Input
Force

Third Class Lever: input
force is in-between the
output force and the
fulcrum.
 MA is always less than 1
 Ex: tweezers, staple
remover, broom
 Pulley: a machine that
consists of a wheel that
turns freely in a frame
called a block.
 A pulley can be used to change the
direction of a force or to increase input
force depending on how the pulley is
arranged.
 Fixed Pulley: changes the
direction of a force;
however it does not create
a mechanical advantage.
 Example: Elevator
 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 ropes
that support the
moveable pulley.
 Wheel and Axle: a simple
machine consisting of a
larger wheel rigidly
secured to a smaller wheel
or shaft, called an axle.
 When either the wheel or axle turns,
the other rotates with it.
 One full revolution of either part causes
one full revolution of the other part.
 Examples:
 Pencil sharpener
 Door knob
 Faucet handles

Inclined plane: is a sloping surface that
reduces the amount of force required to do
work by increasing the distance over which
work is done.
 The inclined plane makes it easier to move a
weight from a low height to a high height.
 Wedge: an inclined plane that has one
or two sloping sides.
 It changes the direction of the input force.
 Examples:
 Knife/ax
 Door stopper
 Screw: an inclined
plane wrapped in a
spiral around a post.
 The threads form a tiny
ramp that run upward
from its end.
 Example:
 Many types of lids
 Screws
 Two or more simple machines
operating together.