A plank and a block of wood can become a lever system which makes it easier to lift heavy objects.
Pulleys help with lifting things too.
Levers make lifting easier.
The length of the lever and the position of the turning point, or ‘pivot’ are important.
Pulleys convert downward ‘pull’ into upward ‘lift’.
Pulleys reduce the effort needed to lift a load.
Levers and pulleys belong to that class of items known as simple machines.
Simple machines are able to multiply a force and control the direction and strength of the force to make moving objects easier.
They are able to concentrate the moving force to where it is needed.
Levers can make it easier to move things.
With some levers, the object to be moved is at one end of the lever and push or pull is exerted on the other end.
There are different kinds of lever but all levers need a point about which the lever can turn (the pivot).
Where the pivot is positioned is important.
Some types of lever convert a small force at one end into a larger force at the other.
The strength of the levering force is affected by the position of the pivot.
With some levers, eg. A nutcracker, the pivot (or fulcrum) is at the end and there are two lever arms which work together to get the job done.
Animals sometimes communicate by touch.
Parent animals often comfort their young through touching.
Touching is important for most young animals. Animal courtship routines often involve touching.
Sometimes this is ritual behavior.
Sometimes the touching is functional.
Touching between human beings can be a powerful form of communication and also a way of passing on a personal message.
Touching plays critical roles in human social relationships including infant bonding and attachment, caretaking, aggression, courtship, sexual relations, first impressions, children’s interactions, and in medical settings.
Touching is crucial for the healthy development of babies and is one of the main ways in which they learn about the world.
Rainbows are caused by the effect of sunlight on water drops.
White light (sunlight) is a combination of all colors (the colors of the rainbow).
Triangular blocks of glass can split white light into this different colors, giving the same effect.
Prisms and raindrops bend sunlight as it enters.
This splits the white light into its component colors.
These different colors are reflected off the back of the raindrop and out again towards the viewer. This is what the viewer sees.
The viewer needs to between the sun and the water droplet.
The old magical belief that there is a pot of gold at the end of the rainbow can never be so. As you move, so does the vantage point from which you are seeing the rainbow, and the rainbow itself will either move too, or disappear altogether.
Sound travels through air.
Ears are designed to detect sound.
Sound can travel through some solid materials.
Sound is made when things vibrate.
Sound vibrations travel through the air.
These vibrations can make other things vibrate.
Vibrations traveling through solid materials can be detected by the sense of touch.
Ears are complex and delicate organs.
The outer ear functions like a funnel, collecting sound vibrations and passing them along the ear canal until they strike the eardrum, causing it to vibrate.
The eardrum (or tympanic membrane) is thin enough to transfer vibrations to the bones in the middle ear. The auditory nerve, connected to the inner ear, then transmits these vibrations to the brain where it is interpreted by the auditory centers.
Using a special instrument (an oscilloscope) allows sound to be ‘seen’. Different sounds make different patterns on the oscilloscope screen.
An oscillloscopse converts sound vibrations into visual patterns on its screen. These patterns appear on the screen as a series of waves.
The lower the note, the slower the vibration and the further apart the wave pattern is.
Higher notes form wave patterns which are smaller and closer together because the vibrations are faster.
Musical instruments parallel this.
Instruments that are used to play deep notes tend to be large, to handle the vibrations (eg. Double-bass, tuba, baritone saxophone) whilst high note instruments tend to be smaller (flute, recorder, clarinet).
Loud sounds can damage the hearing ability of ears.
Ear-defenders protect ears by cutting down the intensity of sound that reaches them.
Ears are sensitive organs and have limits to the amount of sound they can safely handle. Exceeding these limits can damage the ears, in some cases permanently.
Ears need to be protected from these risks where sustained and excessive sound is present.
The longer the exposure to excessive sound the greater the risk of ear damage. The eardrum or tympanic membrane), which vibrates as sound is carried to it, is very thin.
It is only able to tolerate vibrations to a set limit.
Sound that is too loud causes the eardrum to vibrate beyond its endurance and can make it rupture.
Animals have five senses: seeing; hearing; touching; tasting and smelling.
Each sense organ has a particular function.
Senses allow animals to detect what is happening in the world around them. The senses detect stimuli.
Different stimuli produce different reactions.
The senses are used for a variety of different purposes.
In humans, messages from our senses (eg. Touching a hot stove with our fingers) are sent through the central nervous system to our brains for processing. The brain then sends messages back to those parts of the body that need to react (eg. Move hands away before they get burned).
This whole process only takes a fraction of a second to occur.
Objects fall to Earth.
Parachutes are designed to allow the human body and other objects to fall to the Earth slowly. Jumping without a parachute from an aeroplane would be a disaster.
Parachutes are very unstreamlined.
They increase air resistance and decrease the rate of fall.
Making model parachutes and dropping them is a good way of experimenting with air resistance.
Objects fall through air to the ground by the force of gravity acting on them. At the same time that gravity is pulling the falling object downwards, the air through which the object is falling is pushing upwards.
The more air that can be captured by the falling object, the slower will be its fall toward the Earth.
Smooth shapes travel through air and water more easily than shapes that are not smooth.
All objects moving through air and water encounter resistance.
This resistance, called ‘drag’, is caused by a fluid (such as air or water) pushing against an object, causing the object to move less rapidly through that fluid.
Smooth (streamlined) shapes overcome the effects of ‘drag’ more effectively. They allow air to move around them more easily.
The movement of air around objects can be observed with smoke trails in wind tunnels.
Fast transport vehicles are designed to reduce ‘drag’.
Some animals are streamlined to suit the lifestyles in which they live.
Making models of ‘real life’ machines is a good way of investigating how they work.
Machines need some form of power to make them work.
Simple materials can be used for making models.
Models do not always exactly mirror the real object.
‘Low technology’ may look simple, but it can be very efficient.
Machines can be made out of everyday, local materials.
Human populations and needs can frequently be answered by technology. The problem of getting a fresh supply of water can be lessened by the use of fairly simple devices.
Since a push is easier on the human frame to administer than a pull, machines that use pushes, rather than pulls, make our lives easier.
Animals that work for us are also pushing (against their harness) though people often see them as pulling.
Animal bodies are held in shape by their skeletons.
Skeletons are made from lots of bones.
Bones do not bend. Movement in skeletons happens at joints.
Muscles control movement of joints.
Muscles can only work by pulling on bones.
The muscles contract (shorten) as they pull.
Muscles usually operate as opposing pairs.
Like machines, our bodies consist of a framework with moving parts.
Joints are like turning points (or pivots) of levers.
One muscle, or a set of muscles, contracts and pulls on the bones to cause movement.
This muscle cannot push the bone back again, but another muscle, or a set of muscles, is used for this.
Animals’ eyes may work differently from ours, but they may see the same as we see.
It is what the brain makes of what the eye sees that is important.
An animal’s eyes are particularly suited to its life-style and the environment in which it lives.
The position of an animal’s eyes and the type of lens the eye has give clues as to how it may view the world.
Birds, whose eyes assist them in hunting, navigating and avoiding predators, have some of the sharpest eyesight in the animal kingdom.
Their eyes are very large, sometimes weighing more than their brains.
Some hawks and eagles have eyes which are about the same size as an adult human’s.
Lands snails have eyes at the tips of long tentacles which they use to explore terrain.
There is a great variety of eye types in the animal kingdom.
Magnifying lenses and microscopes help in seeing small things.
Binoculars and telescopes help in seeing distant areas or objects.
There are special devices to help us see in the dark or inside the body.
Many aids to vision use lenses.
Lenses can have the effect of enlarging the view of an object.
Lenses can also have the effect of bringing a distant object closer.
Lenses come in two basic shapes; concave and convex.
Concave lenses are thin in the middle and thick at the edges, and spread out the rays of light that pass through them.
This makes objects appear smaller or further away than they are.
Convex lenses are thick in the middle and thin at the edges.
They converge rays of light and make objects appear larger or closer than they are.
Focusing is important when using lenses.
X-rays can show bone but not skin and flesh.
Infra-red viewfinders enable objects to be seen in the darkness.
Animals need to keep an eye on what is going on around them.
They have developed ways of doing this that are appropriate to their life-style and environment.
Eyes are adapted for particular purposes.
These adaptations have evolved to suit the particular needs of the animal in relation to its survival in the environment in which it lives.
Most owls are nocturnal and hunt at night.
The light-sensitive layer of the retina contains two types of photo receptors know (because of their shape) as ‘rods’ and ‘cones’.
Rods register images in black and white, while cones
are responsible for color vision.
Owl eyes are rich in the light-sensitive rods for black and white night vision. However, they have a few cones so they are almost color blind.
All lenses bend light. Convex lenses also focus light, causing magnification of objects viewed through them.
Different curves produce different magnification.
Magnifying lenses have the effect of concentrating, or focusing light.
A strong lens has the effect of making objects seem larger or closer when viewed through it.
Lenses are used innumerous devices to help us to see objects more clearly such as reading glasses, distance glasses, contact lenses, microscopes, magnifiers and magnifying glasses, binoculars and telescopes.
Lenses are also used as devises to focus light images such as photograph cameras, film and video recording cameras, film and slide, and overhead projectors.
Hunters need keep senses to catch their prey.
Most hunters’ eyes face forward.
Hunters who depend on sight need to be able to spot prey at a distance. Hunters need to be able to judge distance accurately.
Animals that hunt have adapted eyes that are well suited for this task. There are some common characteristics among most animals that hunt. Their eyes generally face forward so that they can spot their prey with both eyes at the same time.
They are able to locate their prey from a distance.
They are able to judge distance with great accuracy, by focusing with both eyes on the same object at the same time.
Even with these similarities, different predators have different hunting styles. While hunters need too eyesight, it is also an important asset for the hunted!
Sign language can be useful.
For some people, sign language is essential.
Signals and sign language can be useful where speaking and hearing is not possible.
For sign language to have meaning, both the sender of the message and the receiver of the message have to understand what the signals mean.
Some sign languages are complex and can be used for conversation.
Signals are often symbols for words and phrases.
Sign language used by people who have little or no hearing (or ‘signing’ as it is often called) involves making a picture or sign with one or two hands.
The picture often stands for the concept behind the word as well as the word itself.
For example, the sign for ‘big’ can also mean large, huge, enormous, or gigantic, by changing the feeling of the gesture with eyes, face, body and legs.
Animals have the right eyes for the job.
Different animals have differently designed eyes.
Animals’ eyes have evolved to suit their life-style and the environment within which they live.
Their eyes are particularly suited to their needs.
One of the most obvious differences in the eyes of various animals is the placement of the eye itself.
Many birds and fish, for example, have eyes at the sides of their heads, which gives them a greater field of vision that humans have.
They need this wide field of vision to help them escape from their predators. Bottom feeding fish often have eyes on the top of their heads.
Most predators, including humans, have eyes in the front of their heads.
The cannot see things behind, above or beside them without moving their heads.
In white light all colors from the visible spectrum can be seen.
Only some colors can be seen through colored plastic.
Some colored plastics only let one color (their own color) through.
Other colored plastics let several colors through.
Color ‘filters’ only let their component colors pass through.
They absorb all of the other colors from white light.
This is why they are called color ‘filters’. For example, red filters only let red light pass through them, blue only blue light,
and green only green light.
Orange filters let some yellow and some red through because the color orange is made up of partly yellow and partly red.
The light we see is only part of the entire electromagnetic spectrum.
Parts of this spectrum that are invisible to the naked eye include X-rays, ultraviolet rays and infra-red radiation.