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.
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.
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.
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
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.
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.
There is a limit to the load that a bridge can support.
Designs that use triangular shapes and arches can make strong bridges.
Real bridges cannot be tested to destruction.
Making a testing model bridges for strength of design and materials is useful. Structural design and material strength have to be combined to make an efficient bridge.
Where the bridge is, and its intended use, affect the design.
A bridge designer must consider where the bridge is to be located and its intended use.
Construction costs can be an important factor.
In addition to load bearing, bridges have to be strong enough to withstand other forces.
They must be safe in storms and not be adversely affected by rain, snow, ice and intense heat.
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.
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.
The choice of food may be affected by its color.
People may have different preferences of color for certain types of food. Most foods have natural color.
The color of food can be changed artificially with food coloring.
In this sort of test, the results may not be the same every time.
Taste buds are the receptors which determine our sense of taste.
These are nerve endings (about 10,000 of them) found on the tip, sides and back of the upper surface of the tongue.
Most experts use 4 taste receptors: sweet, sour, salty and bitter.
Each kind of taste bud is grouped in a specific location on the tongue.
For example, our ‘sweet’ taste buds are on the tip of our tongue, ‘salty’ on the side, ‘sour’ further back on the side, and ‘bitter’ right at the back of our tongue.
Some animals need a good sense of smell.
There may be different reasons for needing a good sense of smell.
Predators like in wait downwind of their prey so that they themselves cannot be smelled.
Certain smells have meaning for animals.
Smells can indicate food, companions, territory or danger.
An animal’s use of smell has evolved to suit its life-style and the environment in which it lives.
Smells are caused by molecules of a substance entering the nose and reaching the ‘smell detectors’ which are special nerve cells.
These detectors send messages through the olfactory nerve to the area of the brain responsible for interpreting smells.
The brain tells you what you smell.
The senses of smell and taste are closely linked.
That is why we cannot taste or smell very well when we have a cold.
Bodies are sensitive to touch.
Some parts are more sensitive than others.
The fingertips are the most sensitive parts of our hands
The closer together the nerve endings are, the more sensitive the are, the more sensitive the area.
The sense of touch can be utilized to help overcome problems of sight. The sense of touch is very important to human beings and is used, as other senses are, as a means of interpreting the world around us.
Our hands pick up the state (solid, liquid, etc.), texture, and temperature of materials and we can quickly form judgements from this sensory information. One fact which affects our perception of touch is skin thickness, which in humans varies greatly all over the body.