Download Pulley - TeacherWeb

Wheel and
Axle
Screw
Lever
Simple
Machines
Pulley
Wedge
Inclined Plane
Simple machines are useful
because they can make a
physical job easier by changing
the amount or the direction of
the force exerted to do work.
Machine – a tool that
helps us do work
Machines help us by:
1. Changing the amount of
force on an object.
2. Changing the direction of
the force.
Force is a push or pull.
Example: I push a bookshelf to
move it.
Energy is the ability to do
work.
Example: I must have
energy to run the mile.
Work is the result of
force moving an object.
Example – Picking up
something heavy is hard
work!
Load
• the weight that is moved, lifted,
or supported by a simple
machine.
Load
Inclined Plane – a slanted
surface to make lifting
easier
Examples: ramp, stairs
What is an Inclined Plane?
• A ramp is an inclined plane.
• A ramp helps move objects from one
level to another - - higher or lower.
An Inclined Plane is a simple machine that helps reduce
the force needed to move a load.
Instead of picking up this load and lifting it straight
upwards, the load can be pushed along an elevated
plane, which changes the direction of the force.
The user must move the load a greater distance, but the
force needed to move it will be less.
What is a Pulley?
• A pulley is a simple machine with a
wheel and a rope.
• The rope fits around the edge of the
wheel.
• You can use a pulley to move a load
up, down or sideways.
A pulley is made of rope or
string wound around a wheel
to change the direction of a
force.
•
•
•
•
•
•
•
Examples of where pulleys can be used:
Flag Poles
Sailboat
Blinds
Crane
Curtains
Fishing Pole
Pulley – a simple machine consisting
of a wheel with a groove for a rope.
• Fixed pulley is anchored to a single
spot. It can rotate but does not move
up or down.
• Moveable pulley is free to move up
and down.
• Pulley system is a group of two or
more pulleys that work together to
lift a load.
The pulley does not move
Single Fixed Pulley
This pulley lets the user change the direction of
the force, allowing someone to pull down to lift
the load up.
The effort needed to lift this load is equal to the weight of the
load. This is because the load is supported by only 1 rope arm.
You must also pull an amount of rope equal to the height you
wish to lift the load
Single Moveable Pulley
The pulley moves
This pulley system requires only half the effort
needed to lift the weight of the load. If the load
weighs 20 lbs, only 10 lbs of effort is needed to
lift it.
The load is supported by 2 rope arms under the pulley. Each load arm supports
half the weight of the load, so the arm pulling up uses only 10 lbs of effort to lift
this load. You must pull twice as much rope as desired to lift the load a certain
height. Example: Pull 2 ft of rope for each 1 foot of height that you want to lift
the load.
Single Fixed/Single Moveable Pulley
This pulley system combines the properties
of their single components into a system
that changes both the direction of the force
and the amount of force needed to lift the
load.
4
2
3
3
1
1
3
1
2
1
More supporting ropes = less
force required to lift an object
2
4
2
3
3
1
1
3
1
2
1
Supporting rope arms only
pull up, not down.
2
4
2
3
3
1
1
3
1
2
1
Supporting rope arms only
pull up, not down.
2
Simple Machines
allow users to
accomplish work
more easily!