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.
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.
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.
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.
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.
Some animals have to locate their food by touch.
Animals have to be able to find food in different locations.
Some animals have evolved ways of finding their food by using the sense of touch.
Different parts of animals’ bodies may be sensitive to touch.
As animal’s behavior adapted and evolved to depend more and more on their sense of touch, some became able to spend their entire lift in dark environments, either in caves or underground.
For example, various kinds of fish, salamanders, some insects, and crayfish have adapted to totally dark environments. In the dark zone, eyes are useless and many permanent cave-dwellers are blind.
They depend on touch, smell or hearing for moving around. Many locate prey by sensing vibrations.
The ear is divided into three parts: the outer ear; the middle ear; and the inner ear.
The outer part of the ear funnels sound down the ear canal (a tube about three centimeters long) towards the middle ear where the eardrum is locate.
The eardrum vibrates when sound vibrations hit it.
The vibrations are then transmitted through three tiny bones in the middle ear known (because of their shapes) as the hammer, the anvil and the stirrup.
The stirrup bone pushes directly against the inner ear with is filled with fluid.
In the inner ear, the vibrations move through the fluid and cause tine hair-like cells to move.
These, in turn, are connected to other nerve cells which send messages to the brain.
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.
Human sounds are made by using the vocal chords.
Something must move for sound to be made.
Sound is made by something vibrating.
For example, when a bell rings, the sound vibrations vibrate the air, which, when it reaches our ears, make the tiny bones in our middle ear vibrate at the same frequency.
This vibrating message is picked up by the auditory nerve connected to the inner ear, then transmitted to the brain where it is interpreted by the auditory centers.
Altering the vibration changes the sound (it may make it louder or softer, or it may make a change intone or pitch).
Sound travels away from the source of the sound in all directions and can travel through a gas, liquid or solid.
The further the sound vibrations get from their source, the weaker they become
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).
Animals are hard to see if their color matches the color of their surroundings. Some animals can change their color to suit their surroundings.
When the color of an animal matches its surroundings, we say that the animal is camouflaged.
Animals camouflage themselves either for protection or to be less visible to the creatures they are hunting.
Some animals are camouflaged so that their shape and behavior, as well as their color, make them resemble something else in the environment.
These animals do not blend into the environment.
These animals rather they blend with the environment.
Their predators or prey can easily see them, but they are mistaken for other objects.
Females are more likely to be camouflaged than males. It is helpful for females to be inconspicuous since they are extremely vulnerable during the time they spend sitting on eggs or nursing their young.
Braille is a special language which is ready by touch.
It is named after its inventor, Louis Braille.
It enables blind people to read words by touch. Braille is a code where words are written in a series of raised dots and on the surface of paper.
Machines rather like typewriters can be used to produce the language on paper.
For a touch code for letters to be useful, it must be easily reproduced, easily learned by someone who cannot see it and able to be quickly hand-scanned. Braille’s invention met all these requirements enabling blind people immediately to read words, numbers and notation for mathematics, science and music once they had learned the code.
Many books are available in Braille and it is also used in places such as lifts to assist people in locating the correct floor
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.
Light travels into the eyes.
It gets into the eye through a hole at the front.
The size of the hole changes to let in more or less light.
When light hits the back of the eye, the brain interprets what the eyes see. Light enters through the pupil. The iris controls the size of the pupil.
The retina at the back of the eye contains nerve ends which send messages to the brain. Light shining on the eye triggers the reflex of the pupil to constrict. Darkness, in turn, causes the pupil to open up so that it can let in more light. The function of the pupil is to let in no more light than the eye can tolerate, but enough to let the eye work.
The size of the pupil is controlled by a ring of muscles around the iris (the colored part of the eye).
The inside of the eye is filled with a thick, jelly-like material that helps to make the eyeball round, and transmits images through the eye.
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.
Pushes and pulls can be of different strengths.
The size of a push or pull can be measured.
Measuring devices are needed to measure the force of pushes and pulls. Forces are measured in newtons.
Newtons (N) is the scientific unit of measurement used for measuring the strength of a force.
Instruments that can be used to measure force strengths are called ‘force meters’, and they are calibrated in newtons.
It takes about 4N (four newtons) to lift an average-sized book.