INVESTIGATION 3: PULLEYS

WHAT IS A PULLEY? Is a wheel with a grooved rim in which a

rope can run to change the direction of the pull (force) that lifts the load.

HOW TO BUILD YOUR PULLEY

Use the following steps: Clip a binder clip to the end of a half-meter stick. Lay the tick on your desk so that only the clip

extends over the edge. Use a piece of duct tape, positioned close to the

clip, to prevent the stick from sliding side to side.

Put a heavy dictionary on the other end of the stick to hold it down.

TITLE: SINGLE PULLEY SYSTEMSPurpose: To investigate a different type of

simple machine known as a pulley and identify how it makes work easier.

Q?

OBSERVATION Draw, explain, diagram all the pulleys

you can make using the materials you have been given.

FIXED PULLEY Has a wheel that is attached to

something above the load.

SINGLE MOVEABLE PULLEY Has a wheel that is attached to the load

OBSERVATION/ DATA

CONCLUSION What did you learn today?

Did you answer your question?

Were you able to include any new vocabulary?

One Pulley Systems

Line of Learning (LOL)

• A pulley is a wheel with a grooved rim in which a rope can run to change the direction of the pull (force) that lifts the load.

• A fixed pulley has a wheel that is attached to something above the load.

• A movable pulley has a wheel attached to the load (moves with the load)

One Pulley Systems

Line of Learning (LOL)

• Mechanical Advantage reduces the effort (force) needed to lift the load or overcome a resistance; it results from using a simple machine.

• Directional Advantage is a change in direction that results from passing a rope through a pulley

One Pulley Systems

Line of Learning (LOL)

• Do single-pulley systems provide advantage?

– Single-fixed pulley = directional advantage, they change the direction of effort needed

– Single moveable pulley = mechanical advantage, they reduce the effort needed to lift the load

TITLE: TWO-PULLEY SYSTEM Purpose: To discover the advantages of

using pulleys

Q? Is there any advantage to using two pulleys at the same time? Why or Why not.

OBSERVATION How can you build a pulley system using

2 pulleys?

Use what you already know about pulley systems.

OBSERVATION Can you build a system that changes

the direction you are pulling?

LOL

Two Pulley Systems

Line of Learning (LOL)

• Two pulley systems can provide a greater mechanical advantage when lifting a load that having one pulley

• A simple machine is any of the six basic devices that provide mechanical or other advantage like levers and pulley

• The 6 simple machines are– Screw -wheel and axle– Wedge - lever– Inclined plane - pulley

THE PULLEY GAME You will need to work in your groups and

compete against the other tables to build pulleys.

On your mark get set…..

INVESTIGATION 4

Pulleys at Work!

Title: Effort in Pulley Systems

Purpose: To investigate the relationship between the number of ropes pulling on the load and the effort it required to lift the load.

Q? Is there a relationship between the number of ropes supporting the load and the effort required to lift the load?

PREDICTION:

DATA/ OBSERVATION

CONCLUSION Based on your data which pulley do you

believe is giving you the most advantage?

Why?

How do the number of supporting ropes impact the advantage?

What relationships can you see in this chart?

Effort in Pulley Systems

Line of Learning (LOL)

• The greater the number of ropes supporting the load, the less effort needed to lift the load

– More ropes = less effort

• The more supporting ropes you have the less work you have to do

To figure out the effort you need divide the load by the number of supporting ropes.

(Example on next slide)

LOL CONTENT EXAMPLE If I had a load that was 30 N what would

my effort be if I had….

1 supporting rope = ________

2 supporting ropes = ________

3 supporting ropes = ________

5 supporting ropes = ________

6 supporting ropes = ________

Title: Measuring Distance

Purpose: To record and compare the distance moved by the load and the effort in four pulley systems.

Q? Is there hidden cost when we use simple machines, pulleys to lift a load? If so what do you think it is and why?

PREDICTION:

DATA / OBSERVATION

CONCLUSION What are the advantages and

disadvantages to using pulleys?

Measuring the Distance

Line of Learning (LOL)

“You never get something for nothing” applies to pulleys because…..

• The benefits gain (making work easier) by using simple machines are always balanced by cost.

• When the benefits outweigh the cost the machine is a useful tool.

• With pulleys we looked at the number or ropes compared to the distance required to travel….if you had to triple the distance the machine was not a useful tool

PRACTICE WITH DISTANCE