is a wheel with a grooved rim in which a rope can run to change the direction of the pull (force)...
TRANSCRIPT
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.
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.
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…..
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?
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?
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