Mechanisms.
Have you ever wondered how the ancient Egyptians built the pyramids?
They didn鈥檛 move millions of stones using brute strength alone.
Instead, they may have relied on mechanisms, like this pulley and slide system, to pull the stones into place.
Mechanisms are devices that we create to help us.
No matter how simple or complex they are: most mechanisms are designed to change smaller input forces and motion into greater output force and motion.
Some rely on human muscle power to function.
Others use energy provided by different forces, like electricity, wind or hydro power.
There are various types of mechanisms, including:Levers.Pulleys.Wedges.Screws.The wheel and axle.And the inclined plane.
Today, more than 4,000 years after the ancient Egyptians built the pyramids,
mechanisms are everywhere 鈥 supporting our modern way of life in lots of different ways.
They help to power our clocks;and our cars.We use them to construct towns and cities;to make food;even to stay fit and healthy.
Take a look around your home.
What mechanisms do you see?
Maybe you鈥檝e got a toaster in your kitchen 鈥 it uses a spring mechanism to pop the toast.
When it鈥檚 ready, you use a screw mechanism to access your jam.
In what other ways do mechanisms improve your life?
Simple machines do not reduce the total amount of work that needs to be done.
But they do reduce the effort required.
When you open a tin can, for example, the ring pull lifts a lever that breaks the seal by increasing the force at the other end.
The longer the lever, the easier it is to open.
Some machines even use more than one mechanism.
A spade combines a wedge and a lever.
A wheelbarrow is a combination of an inclined plane when it鈥檚 tipped forward, a lever and a wheel and axle.
You can learn more about mechanisms by conducting a pivot point experiment.
You will need a pound coin or a large heavy button.
A piece of fruit, like an apple.
A ruler 鈥 and a pencil to act as the pivot point.
With the pivot point in the centre, observe what happens when you try to balance the pound coin and the apple.
Now move the pivot point closer to the apple.
Even though the pound coin is roughly seven times lighter 鈥 its distance from the pivot, compared to that of the apple, increases the force applied by its weight.
What other types of objects could you use with this lever mechanism?
Video summary
This short animated film explores mechanisms.
Mechanisms are devices that we create to help us. Most mechanisms are designed to change smaller input forces and motion into greater output force and motion.
This film explains what a mechanism is, using examples of where they are used and how they make our lives easier.
This short film is from the 大象传媒 Teach series Explain, Explore, Expand.
Teacher Notes
Explain
Mechanisms, including levers, pulleys and gears, allow us to use a smaller force to have a greater effect and change motion.
Let's explore what these machines are and how they make life easier for us.
Note: Many simple machines are often called tools because tools help us to modify our environment. However, not all tools are machines. When we are discussing tools to multiply or change forces and motion, we refer to them as machines. An everyday tool like a spade is actually a combination of two simple machines, the lever and the wedge.
Key Facts
- Mechanisms are complex machines that change the input forces and motion into a desired output force and motion.
- Example; bicycle. We sit and push on the pedals moving our legs in a circular motion, these are our input forces, and this drives us forward (linear motion) much faster (output), than we can run and with much less effort.
- Machines mean we are no longer relying on muscle power alone. Machines multiply our applied force.
- Complex machines are combinations of two or more simple machines.
- Simple machines do not change the amount of total work that needs to be done, however, they reduce the effort that is required because they increase the distance over which the force is applied
- All machines are based on a combination of these six simple machines.
- Inclined plane - includes ramps, hills, and staircases.
- Wedge - includes knives, kxe heads, door stops, chisels and nails to name just a few.
- Screw - a screw is like a cylinder with an inclined plane that is wrapped around it. Includes: Nuts, bolts and jar lids.
- Lever - levers have a long arm and a fulcrum, which is where the arm pivots (a turning point). The object you are lifting is called the load, and the force you apply to that load through the arm to make the object move is called the effort. So, a lever is the name of the structure that connects these other three parts. Everyday levers help us to lift, move, break, squeeze objects and cut things.
- First-class lever - has a fulcrum in the centre, between the effort 鈥 or force 鈥 and the load. Includes scissors, a seesaw and a claw hammer and a crowbar. Scissors and pliers are a pair of first-class levers which work together.
- Second-class lever - has a fulcrum at one end and a load in the middle. Includes nutcrackers, bottle openers and nail clippers.
- Third-class lever - the force is between the load and the fulcrum. Includes fishing rods and the human arm.
- Pulley - a basic pulley is a wheel on a fixed axle with a groove in it to guide a rope or cable. The pulley changes the direction of or the amount of force that is needed to lift an object. Includes lifts, cranes, and cable cars.
- Wheel and axle - the wheel and axle have two basic parts: the wheel and the axle. They not only change circular motion into straight motion they decrease effort, increase force. By adding teeth to wheels of different sizes we create gears.
- This video references gears. Further information can be found here: 大象传媒 Teach Gears
Explore
Where to pause?
- 00:42 - pause the video. Ask the children to identify some uses of wind, electric and hydropower.
- 01:28 - pause the video. Ask the children to identify some simple machines from around their home.
- 02:50 - pause the video. Ask the children, are there any limits to the differences in the weight of the two objects that would stop a lighter object lifting a heavier one.
Activities / Experiments
- Activity 1: ._
- Activity 2: Investigate pulling objects up an inclined plane with a newton meter as opposed to lifting them directly up. Change the angle of the slope and see what happens.
- Activity 3: Investigate using longer levers to use very light objects to raise heavy objects (Take care with falling objects).
Fun Facts
- The first wheel may not have been used for transport but for pottery.
- Historians think the first wheel and axle was used in either the Middle East or Eastern Europe over 5500 years ago.
- The Greek mathematician, scientist, and inventor Archimedes is said to have promised 鈥滸ive me a lever and a place to stand, and I'll move the world.鈥 He may or may not have said it, However, it would show a deep understanding of the principle of the lever and fulcrum and how it is possible to move extremely heavy objects with much less effort. Archimedes contributed his knowledge to at least three of the simple machines.
Expand
Discussion questions:
- What is an Archimedes screw and how can it lift water?
- Why are gears different sizes?
Other Videos:
Learning Objectives:
- To recognise that some mechanisms, including levers, pulleys and gears, allow a smaller force to have a greater effect. So let's explore how they make life easier for us.
National Curriculum objectives:
- England: To recognise that some mechanisms, including levers, pulleys and gears, allow a smaller force to have a greater effect.
- Scotland: By investigating forces on toys and other objects, I can predict the effect on the shape or motion of objects.
- Northern Ireland: To explore devices that push, pull and make things move. The uses of energy in a variety of models and machines and ways in which energy is used to create movement, for example, pneumatics and hydraulics.
Sources:
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