Canada Science and TechnologyMuseum presents

BIG Motion, Little Effort

All you need is brain power! Lift, catapult and pull heavy objects without even breaking a sweat.

You’ll be amazed at how little effort a lot of fun can be.

EVENT: March Break 2012 –Genius at play
Location:Locomotive Hall

Written by: Isabelle Kingsley on January 22, 2009

Reviewed by: Sandra Corbeil onFebruary 5, 2009

Helen Graves Smith onFebruary 6, 2009

Modification by Catherine Emond, February 2012

OVERALL Activity Objectives

Participants will:

  1. learn about simple machines and how they can help you do heavy work (move objects) by reducing the effort needed
  2. experiment with different simple machines (and simple machines within complex machines) and how they can help us do work(move objects) bytrying them themselves
  3. discover the scientific principles behind some of these simple machines through hands-on activities

Type:Walk-up with three activities; each activity may be done independently of the others.

Outline

Welcome and introduction

- intro should be done anytime new visitors arrive to the station

Activities(any one activity or a combination of activities can be delivered)

  • Be-Lever it or not
  • Don’t Reinvent the Wheel
  • In the Swing of Things

Conclusion

– conclusion should be done anytime visitors are about to leave the activity station

Audience:

  • Ages 4 and up

What you say….

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Background…

Introduction

Big, strong muscles can move heavy objects – but you don’t have to be big and strong for that. You can actually be pretty weak and still be able to move heavy objects…just use your brain power! If you know about simple machines, you can use your smarts and creativity to move almost anything and barely break a sweat!
Let’s see how simple machines can be used, alone or within complex machines, to help us do big work with very little effort.

Be-lever it or not!

Note to guide: Capture the visitors’ attention by asking them to help you open a can of paint. “Excuse me, can you help me open up this can of paint…I can’t get it open!” Visitors will try to help you but will not be able to open it. Ask them if there is anything around that they could use to help them open the can. Visitors may look at your materials and use one of the tools (levers) to open it up. They will just have done the first demonstration of how levers work!
Of course!!! Using a lever can help me do work!
Levers are simple machines that have been used since the stone age….to move big stones perhaps! In ancient Greece, the scientist Archimedes (är’ke-meedeez) once said that if he could find a place to rest a long enough lever, he could move the Earth. Is that really possible?
First, let’s explore what a lever is. A lever is a simple machine that can help us move big loads with little effort. Simple machines make your work easier by enabling you to use less ‘mechanical’ effort to move an object – they give you mechanical advantage. In science terms, the mechanical advantage is the number of times a machine multiplies your effort force.
A lever turns, balances or moves around a certain pivot point called a fulcrum. The fulcrum can be anywhere on the lever – in the middle or closer to either end. You can find levers everywhere around you. A see-saw, the brake handle on a bike, a stick used to pry the lid off a paint can and the hammer claw that pulls out a nail are all levers. Show visitors the props you have and how the lever turns around the fulcrum. You can mention that some Canadian inventions like the Robertson screw driver, the hockey stick and the Canadarm all use levers also.
Levers help us do many things that require a lot of force. To work, some one or something must push or pull the lever to make it work. This pushing and pulling is called force.
Think about how you pried open the can of paint. You put a stick under the rim of the lid and push down on the end. As you push down, the end of the stick is pulling up the lid. It is the same thing when you open a can of pop. Your finger pulls on the loop to push in the tab.
Levers can exaggerate the force of your strength. With a lever, you can push or pull much harder than you can with your bare hands. So what makes a lever such a strong simple machine?
Levers can help you exert a large force over a small distance at one end by exerting only a small force over a greater distance at the other. When you place a load, or the object that you want to move, near the fulcrum and apply effort (or force) farther away from the fulcrum, then you can move that load easily. The greater the distance over which force is applied, the smaller the force required to lift the load. /

Some more detailed info:
The point where you apply the force is called the effort. The effect of applying this force is called the load. The load arm and the effort arm are the names given to the distances from the fulcrum to the load and effort, respectively. Using these definitions, the Law of the Lever is:
Load arm X load force = effort arm X effort force. If, for example, a 1 gram feather were balanced by a one kilogram rock, the feather would be 1000 times further from the fulcrum than the rock; if a 1 kilogram rock were balanced by another 1 kilogram rock, the fulcrum would be in the middle.

Mechanical Advantage

Be-lever it or not!continued…
Note to guide: in this activity, we will focus on the first class lever only, however, if visitors ask about the second and third class levers, you may show them the props available and explain to them what second and third class levers are. Refer to the information found in Appendix A
Let’s try! Do you think that a small child can lift an adult half a meter off the ground?
Invite a small child to try to pick up an adult (don’t let them injure themselves). It’s tough!Ask the child if they can see a “machine” anywhere that would help them do their work. If they don’t spot it by themselves, point out the plank and ask them if they think it “looks” like a machine. Explain that it is called a simple machine because it can help you do work.
Start with the seesaw anchored so that it doesn’t turn and with the arms fully extended equidistance on each side. Stand both the child and an adult on either side on the seesaw. It doesn’t balance – the adult will be lifting the child off the ground. Ask visitors how they might adjust the seesaw so that the child can lift the adult off the ground. Ask the volunteers to get off and adjust the arms by shortening the arm holding the adult (move the fulcrum from under the arm). Point out that by moving the adultcloser to the fulcrum, the child was able to lift him/her off the ground by standing on it. (you can also do this by moving the adult closer to the fulcrum without actually moving the fulcrum itself but moving the adult along the arm). If you move the fulcrum even closer to the adult, you can ask the child to lift the adult by just pushing down on the lever with their arms!
IMPORTANT SAFETY INFORMATION: To do this activity, you MUST have an adult spotting the child and the other adult/larger child. Instruct the volunteers to stand stiffly on the lever so that they keep their balance. Be sure to instruct the volunteers to remain on th lever until the experiment is over and to wait until you tell them to step down. If the volunteer lifting the other person steps down too early, the other person will come crashing down and could hurt themselves. This activity MUST be done with the DIRECT supervision of the guide AT ALL TIMES.
Congratulations! You have succeeded in lifting a load more than twice your size with very little effort at all!
A smaller load (child) at a greater distance from the fulcrum will cause a greater force downwards than a large load (adult) at a short distance from the fulcrum.By moving the adult closer to the fulcrum, the child was able to lift him/her. When you double the distance of the effort from the fulcrum, you can half the force needed to move the load!
So, back to our initial question inspired by Greek scientist Archimedes – is it really possible to move the Earth if we had a big enough lever? What do you think? / 3 classes of levers





Don’t Reinvent the Wheel!
Invite a visitor to sit in the wagon without wheels. Invite another visitor to pull or push the wagon without wheels from one point to another. It is very probable that the visitor will not be able to move the wagon or will do it with a lot of difficulty. Invite the visitor to look around and ask them if they see a machine that would help them move the wagon from point A to point B more easily. If they don’t spot it themselves, point out the wooden dowels and ask them if they think it “looks” like a machine. Explain that it is called a simple machine because it can help you do work.
One of the first simple machines ever invented was the wheel. Before wheels were invented, people had to drag loads across the ground by pushing or pulling. This was hard work! Then, someone had the bright idea to use tree trunks as rollers under heavy objects. This made moving things around much easier.
Invite the visitors to try moving the wagon again, this time using the dowels as rollers on the bottom. Visitors should notice a big difference in the amount of effort it takes them to move the wagon.
As you can see, wheels can make moving heavy objects much easier. When an object is dragged, the rubbing together of the bottom of the object with the ground creates friction. Partly, friction happens when the rough edges of one object snag on the rough edges of another object, and some of the objects' energy has to be used to break off those rough edges so the objects can keep moving.When you place the dowels between the bottom of the wagon and the ground, the wagon is pulled over the dowel. Because the dowel is round, it moves more smoothly and makes less friction.
A wheel works almost the same as a dowel. A wheel is round like a dowel, but instead of rolling under the wagon, the wheel turns around an axle. The axle is in the center of the wheel.
Note to guide: if the visitor has participated in the Be-lever it or not activity on levers, you can explain to them how the wheel and axle work just like a lever and fulcrum. A wheel and axle is a lever that rotates in a circle around a center point or fulcrum. A wheel is a lever that can turn 360 degrees and can have an effort or resistance applied anywhere on that surface. The effort or resistance force can be applied either to the outer wheel (like a steering wheel) or the inner wheel (axle). / Friction
Friction is the force resisting the relative lateral (tangential) motion of solid surfaces, fluid layers, or material elements in contact.

Force diagram for block on ground. Arrows are vectors indicating directions and magnitudes of forces. W is the force of weight, N is the normal force, F is an applied force of unidentified type, and Ff is the force of kinetic friction.

Don’t Reinvent the Wheel Continued…
The wheel and axle is used in many machines that involve transportation, like the locomotives in the locomotive hall and the cars exhibit; however, this isn’t its only purpose. The wheel and axle can be used to help us do all types of work because of the mechanical advantage it can give us. In science terms, the mechanical advantage is the number of times a machine multiplies your effort force.
When you apply force to the wheel in order to turn the axle, like when you turn a steering wheel, the force put out by the axle is increased and distance and speed are decreased. Demonstrate force being applied to a wheel in order to turn the axle to the visitor by using the steering wheel available. When you apply force to the axle to turn the wheel, like when you are riding your bike, the force put out by the wheel is decreased and distance and speed are increased. Demonstrateforce being applied to an axle in order to turn the wheel to the visitor by using the bicycle wheel available.
Knowing this, how can we use the wheel and axle to produce a lot of force without putting in a lot of effort? Solicit answers from the visitors. By moving a big wheel, you can make the axle put out a lot of force. Let’s say our wheel here is 5 times larger than the axle attached to it. By turning the wheel, you can magnify that force 5 times. This means that you can use a wheel to move heavy objects without breaking a sweat. The bigger the wheel compared to the axle, the bigger the mechanical advantage.
Invite the visitors to lift the bag of sand 0.5 meters off the ground (don’t let them injure themselves). It’s tough! Now ask the visitor if they think that they can lift this bag of sand more easily with the help of a wheel and axle. Invite them to attach the bag of sand to the hook attached to the axle by a chain. The visitor can then lift the bag of sand very easily by turning the wheel. Note: you can also have visitors measure the mass of the bag of sand using a spring balance and then use the spring balance to pull on the wheel to lift the bag of sand, then compare the values.
Well done! You have lifted a heavy bag of sand with very little effort! Using a simple machine like a wheel and axle, great work can be done! / Wheel and Axle – Mechanical Advantage
The mechanical advantage of a wheel and axle is the ratio of the radius of the wheel to the radius of the axle. In the wheel and axle illustrated below, the radius of the wheel is five times larger than the radius of the axle. Therefore, the mechanical advantage is 5:1 or 5.


Tid-bit:
Based on diagrams on ancient clay tablets, the earliest known use of this essential invention was a potter’’s wheel used as early as 3500 BC. The first use of the wheel for transportation was probably on Mesopotamian chariots in 3200 BC. It is interesting to note that wheels may have had industrial or manufacturing applications before they were used on vehicles.
Source: Canada Science and TechnologyMuseum - Science Seesaw and Simple Machines
In the Swing of Things
Invite visitors to throw the bean bag and hit the target from a far distance. Although some visitors may be able to do so, some other visitors (younger children) may find it difficult to reach the target.
Marshmallows are light and can be lifted and thrown pretty easily, however, if you wanted to throw a very large rock at a target, like a castle for example, this task would be much more difficult.
About 2300 years ago in China, someone decided to come up with a very ingenious machine to throw heavy rocks called a trebuchet. This machine became a very popular machine during times of war.
During medieval times, the trebuchet was used as a siege weapon because it was able to cast stones of 100kg or more in weight. These stones, when slung from a trebuchet, would shake the strongest masonry and easily break through the walls of a fortress.
Missiles thrown from trebuchets also included sharp wooden poles and darts, fire, casks of burning tar and dung or rotting matter.
How does this all work? Basically, a trebuchet consists of a lever, a counterweight, and a sling.
A lever is a simple machine that can help us move big loads with little effort. A lever turns around a certain pivot point called a fulcrum. In this case (a Type-1 lever), the force is applied to one end, the load is on the other end and the fulcrum sits between the two. Point out the throwing arm on the model trebuchet and point out where the fulcrum is and where the mid point is on the arm, and where the weights are located.
To understand what is happening in a trebuchet, take a look at this lever. Use the lever prop to demonstrate the way levers work. This lever is like a trebuchet arm (a Type-1 lever). For the trebuchet, the force is very large and the loadis very small. Let’s see what happens when we have 2 different loads acting on a lever.
Note to the guide: if the visitors have not already done the Be-lever it or not activity where a child lifts an adult using a lever, do this activity with them to help them understand the concept of the lever. If they have done this activity already, remind them of it before continuing. / Tid-bit:
The word 'Trebuchet' is derived from the Old French word 'Trebucher' meaning to throw over. In England siege weapons, including the Trebuchet was also known as the Ingenium from the Latin word ingenium meaning ingenious device! The Trebuchet is also referred to as the Trebucket.
Source:
Tid-bit - The largest Trebuchet:
The Warwolf, or War Wolf or Ludgar (Loup de Guerre), is believed to be the largest Trebuchet ever made. It was created in Scotland by order of Edward I of England during the siege of the Stirling Castle in the 13th Century.
When disassembled, the weapon would fill 30 wagons. It took five master carpenters and forty-nine other labourers at least three months to complete.
A contemporary account of the siege states, "During this business the king had carpenters construct a fearful engine called the lup-de-guerre (sic., War wolf), and this when it threw, brought down the whole wall."
Even before construction could be completed, the sight of the giant engine so intimidated the Scots that they tried to surrender. Edward, declaring, "You don't deserve any grace, but must surrender to my will," decided to carry on with the siege and witness for himself the power of the masterful weapon. The Warwolf accurately hurled missiles weighing as much as 140 kg and leveled a large section of the curtain wall.
Source:
In the Swing of Things continued…
A sling is added to the end of the long arm to add even more length to the throwing arm, and gives a projectile more energy which allows it to be thrown further and harder.
Finally, a counterweight is added to the short arm of the trebuchet. As gravity pulls a heavier weight down on one side of the seesaw, the lighter weight on the other side of the seesaw's fulcrum is lifted. So, when the trigger is released, the counterweight begins to drop. This moves the other end of the arm very quickly and the projectile in the sling is flung towards the target. Use the trebuchet as a visual aid as you explain how it works.
Invite visitors to try firing the trebuchet to see how far it can project a marshmallow. Encourage them to try to hit the target with the marshmallow. Guides must load and cock the trebuchet and visitors can fire it with the assistance of the guide. SEE IMPORTANT SAGETY INFO TO THE RIGHT.
Great work! You have successfully fired a real trebuchet. Simple machines really can help you do heavy work with very little effort. / IMPORTANT SAFETY INFO:
The trebuchet models pack a lot of energy and could potentially injure a guide or visitor if used incorrectly. For this reason, ensure DIRECT supervision of the use of the trebuchets. Guide must load and cock the trebuchet and assist visitors in firing the model. Make sure you have received training from the Education and Interpretation officer or the Assistant before attempting to load and fire these siege models.
A few points to keep in mind:
  1. Keep the machines clamped onto a table. This will prevent them from jumping when the forces are released.
  2. Only throw soft objects (marshmallows, bean bags, foam balls, etc). Never throw marbles or ball bearing.
  3. Use triggers and release mechanism when firing (never hold and release the throwing arm with your hands). These triggers are designed to keep your fingers away from moving parts!
  1. Never fire the siege machinery at anyone.

Conclusion

It’s amazing what can be done with something as simple as a simple machine. Moving anything can become a scientific experiment and a chance to be creative. You can see many simple machines during your visit. Check out the wheels on the locomotives and the cars exhibit or the levers in the Canadarm in ISS.
Next time you have to move something big or heavy, rack your brain – don’t break your back. Use what is around you – simple machines are everywhere!

Vocabulary

English

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French

Lever / Levier n.m.
Mechanical advantage / Effet méchanique n.m.
Fulcrum / Point d’appui n.m.
Load / Charge n.f.
Friction / Friction n.f.
Wheel / Roue n.f.
Axle / Axe n.m.
Trebuchet / Trébuchet n.m.
Sling / Sangle n.f.
Counterbalance / Contrepoids n.m.
Projectile / Projectile n.m.

Reference: «Le grand dictionnaire terminologique» (