Pulleys

Pulleys

Another day, another simple machine

● A pulley is one of six classical simple machines.

● Pulleys can be used to lift

objects, apply forces, transmit power, and change the direction of the effort force.
Six classical simple machines

Speaking of classical simple machines...

let's start with review

Multiple Choice

Which is not a type of simple machine?

• spring

• screw

• pulley

• wedge

Multiple Choice

If you use a crowbar to get the lid off of a bucket, what simple machine are you using?

• inclined plane

• pulley

• wheel and axle

• lever

Multiple Choice

How does a driver use a steering wheel as a simply machine?

• The driver is using a wheel and axle to reduce the amount of force.

• The driver is using a lever to steer the vehicle.

• The driver is using a pulley and lever to steer the vehicle.

• The driver is using a wheel and axle to reduce the amount of work needed to steer the vehicle.

Multiple Choice

The lever class in the picture is _?_.

• 1
• 2
• 3

Multiple Choice

The lever class in the picture is _?_. PICK no. 3.

• 1
• 2
• 3

Multiple Choice

The lever class in the picture is _?_.

• 1
• 2
• 3

Multiple Choice

This is an example of what type of simple machine?

• inclined plane

• wheel and axle

• screw

• lever

Multiple Choice

The fixed point that a lever sits on is called the

• pulcrum

• axle

• fulcrum

• wedge

Multiple Choice

What term describes the fixed point around a which a wheel and axle rotate?

• hub
• center
• pivot
• fulcrum

Multiple Choice

What are the 6 types of simple machines?

• hoist, lever, wheel and axle, screw, wedge, inclined plane

• pulley, lever, wheel and axle, shrew, wedge, declined plane

• pulley, lever 2000, wheel and rod, shrew, shoehorn, declined plane

• pulley, lever, wheel and axle, screw, wedge, inclined plane

● A machine is a mechanical device or

object that uses energy to perform
work. A machine will transfer energy
from an input amount of work to an
output amount of work.

● The input and output work are always

equal, but the force applied to both can
be different.

Multiple Choice

A force multiplier is

• a simple machine that can spin very fast

• a simple machine that allows a small force to move a larger object

• a simple machine that increases the distance or speed travelled by an object

• a screw driver

Multiple Choice

A distance multiplier is

• a simple machine that can spin very fast

• a simple machine that allows a small force to move a larger object

• a simple machine that increases the distance or speed travelled by an object

• a screw driver

Focusing on Pulleys

The earliest known pulleys were used in
Mesopotamia (present-day Iraq) in the early
second millennium BCE. 

They were also used in ancient Egypt starting from around 1800 BCE. 

The Greek mathematician Hero of Alexandria identified the pulley as one of six simple machines that could be used to lift weights around the year 50.

​

​Pulley History

Hero of Alexandria –
A Greek mathematician
who lived in Alexandria, Greece, from 10-70
AD.

● He is considered by many to be the greatest experimenter of ancient times.

● He recognized the pulley as one of the

most effective simple machines used to lift objects.

● A pulley is a wheel on an axle that rotates

with the movement of a cable along a
groove at its circumference.

● It is designed to support movement and

change of direction of a cable or belt or
transfer of power between the shaft and
cable or belt.

A pulley is often used to

lift heavy objects

Multiple Choice

What is a pulley?

• the opposite of a pushey- DO NOT PICK THIS ONE

• a wheel on an axle that rotates with the movements of a cable on its circumference

• a wheel on an axle that rotates with the movements of a cable on its diameter

• something other than a simple machine

● It makes work seem easier

because the direction of
the applied effort works
with gravity.

● A pulley may include a

rope, belt, chain, or cable.
Pulleys can be used in a
variety of ways, including
to lift loads, apply forces,
and transmit power.

+ gravity

When a downward force is applied to one side of the pulley, the other side of the pulley with the resistance force is pulled upward. This is called a fixed pulley.

The simplest pulleys are used to reverse the direction of the effort force. In this case, a single pulley is attached to a non-moving surface with a cable or rope running through it.

Simple Pulleys

The object will move the same distance that the rope is pulled by the effort.

Simple Fixed Pulleys

Multiple Choice

To move an object with a simple fixed pulley 3 feet up, what distance and direction will you need to move the attached rope?

• 6 feet right

• 3 feet down

• 9 feet down

• 1 foot down, 1 very large smelly foor

Pulley Mechanical Advantage

The ratio of the output force to the input force. The ideal mechanical advantage is the mechanical advantage in an ideal world. The ideal mechanical advantage of a single movable pulley is two. The ideal mechanical advantage of a single fixed pulley is one. 

Open Ended

What is mechnical advantage?

Multiple Choice

What is the ideal mechanical advantage of a single FIXED pulley?

• 2
• 3
• 4
• 1

● Pulleys can also be assembled as

part of belt and chain drives to
transfer power from one rotating
shaft to another.

● A combination pulley combines a

simple and movable pulley. It
increases the applied force

compared to a fixed pulley.

Do you think the students could lift their principal without the pulley?

Pulley Types

This consists of one fixed block and one movable block that’s attached to the load that’s to be moved.

​Block And Tackle

This involves a set of pulleys that are designed to rotate independently while on the same axle to form a block.

Moveable Pulley

QUICK CLIP

Multiple Choice

What force will be required to pull a 30-pound load up using a pulley system with a mechanical advantage of 2?

• 20 pounds
• 15 pounds
• 60 pounds

• 25 pounds

Multiple Choice

What rope length will be required to pull a 30-pound load up using a pulley system with a mechanical advantage of 2?

• half the distance

• three times

• two times

• 6 times the distance