science education teaching booklet

Name:________ A skate board is given a push What makes the skate board start going? What makes the skate board Keep going? What makes the skate board stop? Are all moving objec ts being pushed Concept: A Force can be defined as a push or a pull 2 Whenever you push, pull, twist or turn something you are exerting a force. A force can start a stationary object moving, :or cause a moving object to come to rest or change its direction or speed. Forces can also change the shape of objects. Throwing a ball, riding a bike, walking, dressing and chewing all involve pushes, pulls, twists or turns. There are many types of forces but they can be divided into two groups, contact forces and non-contact (or field) forces. Contact forces are exerted when objects actually touch one another. Examples of contact forces include: • Tension (the force in a rope during a tug of war) • Upthrust or buoyancy (the force that pushes back on gravity when an object floats) • Friction (the force between the road and the tyres of a car). Non-contact forces can have an effect without objects touching. They can act from a distance. Examples of non-contact forces include: • Gravity (a pulling force between all matter) • Magnetic force (a force which can pull or push magnetic materials) • Electrostatic force (a force which can pull or push charged materials). Experiment: Measuring forces Aim: To make and use a force meter using a rubber band and masses. Materials: • A thin strip of timber or a ruler • a mass carrier • masses Method: 1. Take a 30 cm piece of thin timber and calibrate it as shown in figure below. 2. Make a small groove on top of the timber. Attach the rubber band to the groove and hang 100 g mass to the rubber band. 3. Note how far the rubber band stretches when 100 g is attached—that amount of stretch shows the force (1 N) needed to pull an object weighing 100 g. Remember 100 g = 1 N. Complete the scale up to 5 N. 4. Use the force meter to measure the size of the following forces: • force needed to pull the door open • force needed to drag a chair across the floor • force needed to open a drawer in the laboratory • force needed to move your pencil case • force needed to pull up your sock. 3 Results: Objects measured Open the door to the room Drag a chair across the floor Open a drawer in the laboratory Move your pencil case Discussion: 1. Which of the actions needed: a. More force? ___________________________________________________________________________ ___________________________________________________________________________ b. Less force? ___________________________________________________________________________ ___________________________________________________________________________ 2. Did you experience any problems during your experiment? ___________________________________________________________________________ ___________________________________________________________________________ 3. If so, explain how you would improve the construction of the force meter. ___________________________________________________________________________ ___________________________________________________________________________ Conclusion: (Summarise how you constructed and used the force meter) ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ Force required (N) 4 Question 1. Look at the diagrams below. Which show a push, and which show a pull? Picture A B C D E F Push/Pull 2. Rank these forces in order, from biggest to smallest: 1 to 5 Truck hitting a pole Rocket being launched Typing a letter on a computer keyboard Kicking a soccer ball Pushing a car along the street 5 3. State which of the following actions involve push force, pull force or no force. Actions Opening a window Turning a screw a with a screw driver Smelling food cooking Moulding clay in an art lesson Hitting the enter key on a computer keyboard Standing on a diving board Watching a candle burn Throwing a ball Turning a page in a book 4. Complete the sentences below. Choose from these words: (a) A force is a_________ or a _______________ (b) When you close a door, you _________________ (c) When you lift something, you _________________ (d) Force can make things ___________________ DIRECTION PULL MOVE PUSH Push, pull or no force (e) A force can also make moving things change ______________________ 5. The figure to below shows some forces in action. The forces are shown with arrows. For each picture: (a) Name the object that the force acts on; eg. in A, the force acts on the cart. 6 (b) Choose from the list below to say what the force is doing. What the force is doing starting an object moving stopping an object that is moving changing the direction of movement balancing another force, and preventing movement stretching an object Object (A,B,C,D,E) Contact Forces Concept: 7 Friction is a force that slows down or prevents movement. Friction is the force applied to the surface of an object when it moves against the surface of another object. Both surfaces do not have to be moving. Friction acts where the surfaces touch. Friction can slow down an object or stop it from moving. Friction limits how fast you can go. Rough surfaces produce more friction than smooth ones. To slow down quickly on roller blades you need to use a stopper so that there is more friction. If there was no friction, you would not even be able to start moving forward. However, if there was too much friction, it would take too much effort to keep moving. Experiment: Measuring Friction Aim: To measure the force of friction on different surfaces. Materials: • block of wood with hook attached • your force meter Method: 1. Use your force meter to push a block of wood across your desktop. As long as you push steadily, the reading on the force meter will be equal to the force of friction on the moving block. Record your reading in the results table. 2. Repeat your measurement two more times on the desktop and calculate the average force of friction. Record all data in the table. 3. Repeat this procedure on several other surfaces. Surfaces that you might test are: vinyl floor, carpet, doormat, concrete and bitumen. Results: Friction on different surfaces Surface Force of friction (Newton) Trial 1 2 3 Average 8 Summarise your results in a bar graph Discussion: 1. List the surfaces in order, from greatest friction force to least ___________________________________________________________________________ ___________________________________________________________________________ 2. What feature of a surface seems to determine the amount of friction? ___________________________________________________________________________ ___________________________________________________________________________ 3. Why was it a good idea to repeat each measurement three times? ___________________________________________________________________________ ___________________________________________________________________________ 9 4. Design and carry out an experiment to find out the effect of mass on the size of the friction force. Record your results in a table and display them on a line graph. ___________________________________________________________________________ ___________________________________________________________________________ 5. Do heavier objects experience more friction? ___________________________________________________________________________ ___________________________________________________________________________ Conclusion: (Relate the aim ane the concept of friction) ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ Question 1. What sort of friction (sliding, rolling or fluid) occurs in the following situations? (a) A man pushes a cupboard across the floor.___________________ (b) A bowling ball moves down a bowling alley.____________________ (c) The Space Shuttle re-enters the Earth's atmosphere.__________________ (d) Kurt rides his skateboard._______________________ (e) A surfer waxes her board, then goes surfing. _______________________ 2. In rainy weather the radio sometimes announces that there is a wet weather alert. Why do motorists have to be careful when the roads are wet? ___________________________________________________________________________ ___________________________________________________________________________ 3. Why do cars that travel in snow have to carry chains that fit around the tyres? ___________________________________________________________________________ ___________________________________________________________________________ 4. Why don't bicycle hand brakes work as well when it rains? ___________________________________________________________________________ ___________________________________________________________________________ 10 5. Look at the diagrams below. Complete the sentences by circling the correct word. (a) Diagram A shows (sliding/rolling) friction. (b) The friction in B is (more/less) than in A. (c) Rolling friction is (greater/less) than sliding friction. (d) When an object slides, there is (more/less) resistance to movement than when it rolls. (e) With lubrication (Diagram C) you need (more/less) force to move an object. (f) Lubrication (increases/decreases) friction. 6. Copy and complete the paragraph below, choosing from these words to fill the gaps. Things move more easily along a _______________ surface than a _______________ surface. This is because of friction. It happens when one surface ______________ on another. Rough surfaces like _______________ make ____________friction than smooth surfaces like___________________ CARPET FORCE ROUGH MORE GLASS RUBS SMOOTH LESS Buoyancy Archimedes' Principle after the person who first stated it. Concept: The upward force is called the buoyant force or up-thrust because it acts upwards against the weight of the object. Experiment: Feeling the force of water AIM: To feel the force that water exerts on objects. MATERIALS: 11 • balloon • basin or bucket big enough to contain • the inflated balloon METHOD 1. Blow up the balloon and tie off the neck. 2. Half-fill the basin with water. Place the balloon on the surface of the water so it floats. 3. Try to push the balloon into the water so that it is completely submerged. DISCUSSION 1. How much of the balloon was above the surface of the water when it was floating? ___________________________________________________________________________ ___________________________________________________________________________ 2. What was resisting you when you tried to push the balloon completely under the water? ___________________________________________________________________________ ___________________________________________________________________________ 3. What happened to the level of the water in the bucket as you pushed the balloon further down? ___________________________________________________________________________ ___________________________________________________________________________ Why do you feel almost 'weightless' when swimming in water? What we feel as an up wards 'push' is called buoyancy. This buoyancy is greater in water than in air because water is denser than air. Saltwater has a higher density than fresh water so the buoyancy effect is greater and you float better, or feel more buoyant, in salt water. Aquatic animals can easily swim around in water but some are crushed by their own weight on land. For example, jellyfish float in seawater but are flattened when stranded on the beach. Surface tension is what keeps a water strider from sinking and drowning. The small weight of the water strider is well spread out over the surface and is not large enough to push the water particles apart. Concept: Surface Tension is the pulling of particles in a liquid together Experiment: Holding It All Together Materials: Coin Eyedropper Beaker Dishwashing detergent• Method: 12 1. Estimate how many drops of water you could get onto a 5-cent coin without water spilling over the edge. With great care and from a very small height, test your prediction with an eyedropper. 2. Repeat your test using water from a small beaker with a few drops of dishwashing detergent added to it. Results: Prediction = Trail 1 Number of drops with water Number of drops with Dishwashing detergent DISCUSSION 1. What difference does the detergent make to your result? ___________________________________________________________________________ ___________________________________________________________________________ 2. Were you surprised by your results? ___________________________________________________________________________ ___________________________________________________________________________ 3. What seems to keep the water on the coin? Trail 3 Trail 3 Average ___________________________________________________________________________ ___________________________________________________________________________ Non-Contact Forces Concept: 13 Like poles repel Unlike poles attract Experiment: Magnetic forces Aim: 1. To test which materials are magnetic and non-magnetic? 2. To test forces between two bar magnets. Materials: Copper, paper, lead, rubber, wood, steel, magnesium, aluminium, plastic, zinc, paperclip, iron nail, 2 bar magnets, string, retort stand and a clamp. Method: Part 1—Magnetic or non-magnetic? 1. Place the materials given to you on a small tray. Take a bar magnet and test each material to see if it is attracted by both ends and the middle of the magnet. 2. Record your results in table 1. Part 2—Testing forces between magnets 1. Use a string to suspend a bar magnet from the retort stand. Take the north pole of the free magnet near the north pole of the suspended magnet and see what happens. 2. Repeat this procedure with the south poles. 3. Repeat this procedure with two unlike poles. 4. Record your results in table 2. 14 Results: Table 1—Magnetic and non-magnetic (place a tick in the relevant column) Material Copper Magnesium Paper Zinc Lead Aluminium Rubber Plastic Wood Paper clip Steel Iron nail Attracted Not attracted Table 2—Forces between magnets Poles tested N-S S-N N-N S-S Discussion: 1. Which materials were magnetic? ___________________________________________________________________________ ___________________________________________________________________________ 2. Which materials were non-magnetic? ___________________________________________________________________________ ___________________________________________________________________________ 3. Which part of the magnet was strongest in attracting materials? ___________________________________________________________________________ ___________________________________________________________________________ 15 Attracted or repelled Conclusion: (Complete the following statements) 1. __________________substances are attracted to a magnet and __________________substances are not. 2. Like magnetic poles _______________each other and unlike magnetic poles _________________ Magnetic forces affect only those materials that contain iron, nickel or cobalt. Alloys that contain these metals, e.g. steel, are also affected. Magnets are made of materials that contain one or more of these metals. You will have found that the ends of a magnet are more magnetic than the middle. These are the poles of the magnet. If you suspend a magnet it always points north-south. The end that points north is called the north pole. The other end is called the south pole. If the north poles of two magnets are placed near each other, they will repel each other. Similarly for two south poles. On the other hand, the north pole of one magnet will attract the south pole of another magnet. Concept: Magnets are made of iron, nickel or cobalt Magnetic material are attracted to a magnets Question 1. Complete the sentences below. a. A substance which is attracted to a magnet is said to be____________________ b. A magnet can exert a ____________________________ on a piece of iron without touching it. c. Magnets can be made of ____________ or ___________ or_____________ d. All magnets have two_____________ e. One end of a magnet is called the _________ ___________. The other end is called the f. _________ ___________. g. Two south poles or two north poles are called _________ ________. h. When two magnets push each other apart we say they ___________ i. Like poles __________ , and __________ poles repel. 16 2. Use the words magnetic and non-magnetic to explain why a mixture of steel and brass screws can be separated using a magnet. ___________________________________________________________________________ ___________________________________________________________________________ 3. Are these statements true or false? Statement Any metal object can be picked up by a magnet. A magnet is strongest at its middle. A north pole will attract a south pole. Like poles attract each other. As you move away from a magnet the magnetic force decreases. True/false 4. A piece of iron is magnetic but it may not be a magnet. What does this mean? ___________________________________________________________________________ ___________________________________________________________________________ 5. Complete the table below, by writing 'repel' or 'attract' to say what happens when the poles meet. NORTH NORTH SOUTH SOUTH 6. Look the figure below and then answer the question by circling the correct answer. 17 a. The hand in the figure is holding the south pole close to the (north/south) pole of the hanging magnet. b. The poles that are close together are (like/unlike). The poles will (attract/repel). Experiment: Making An Electromagnet Aim: To make an electromagnet, and investigate how it can be made stronger. Materials a. a small compass b. a large nail (about 8 cm long) c. 2 thin, insulated wires with fitted alligator clips(one wire about 1 m long, and the other about30 cm) d. a 6 V torch bulb and holder e. a power supply f. a box of paperclips Method 1. Wrap about 20 turns of wire around the large nail. 2. Use the wires to connect the nail to a power supply, through a 6 V bulb, as shown in the figure below. (The bulb stops the fuse in the power supply from 'blowing.) 3. Set the power supply to 2 volts DC. Turn it on. • Has the nail been magnetised? That is, will it pick up tacks? How many? ___________________________________________________________________________ ________________________________________________________________________ • What happens when you turn off the power supply? ___________________________________________________________________________ ___________________________________________________________________________ 4. Turn the magnet on again, and bring a small compass near the sharp end of the nail. Use the figure below to decide whether the sharp end of the electromagnet is a north pole or a south pole. 18 5. Test the other end of the electromagnet. 6. Reverse the connections to the power supply. 7. Test the information in the results tables. Result: Number of turns 10 20 30 40 50 60 Voltage A (2 V) B (4 V) C (6 V) D (8 V) E (10 V) F (12 V) Number of paper clips Number of paper clips 1. Why is an electromagnet called a 'temporary magnet'? ___________________________________________________________________________ ___________________________________________________________________________ 2. How can the poles of the electromagnet be reversed? ___________________________________________________________________________ ___________________________________________________________________________ 3. List two ways of increasing the strength of an electromagnet. ___________________________________________________________________________ ___________________________________________________________________________ Question 1. The data table below shows the results of some experiments. The twelve electromagnets are all different, but their cores are the same size. You can tell how strong each electromagnet is by the number of paperclips it lifts. When the electricity is switched off, the paperclips drop from the iron-cored electromagnets, but not from the steel-cored ones. Electromagnet Core Material Number of turns in Voltage (volts) Number of paper clips 19 Questions and conclusions coil 1 2 3 4 5 6 7 8 9 10 11 12 iron iron iron iron iron iron iron iron iron iron steel steel 10 20 20 20 20 20 20 20 20 30 20 30 2 1 2 3 4 5 6 7 8 2 3 2 lifted 2 3 4 10 17 22 26 28 28 6 7 5 a. How can you tell how strong each electromagnet is? ___________________________________________________________________________ ___________________________________________________________________________ b. Write down three things that could affect the strength of an electromagnet. ___________________________________________________________________________ ___________________________________________________________________________ c. Which electromagnets would allow you to find out how the strength depends on the voltage? ___________________________________________________________________________ ___________________________________________________________________________ d. Draw and complete the graph on the left for iron-cored electromagnets with 20 turns in the coil. Is it true that the higher the voltage, the stronger the electromagnet? ___________________________________________________________________________ ___________________________________________________________________________ e. If you wanted to find out how the number of turns affects the strength, which three magnets would you compare? Why did you choose them? How does the number of turns affect the strength? ___________________________________________________________________________ ___________________________________________________________________________ f. Iron is a better core material than steel. Give one reason why. ___________________________________________________________________________ ___________________________________________________________________________ 20 Concept: •Unlike charges attract •Like charges repel •Charged object attracts an uncharged object Experiment: Investigating electrostatic charges Aim: To produce static electricity. Materials: A balloon, a Perspex rod, pieces of wool and silk, small pieces of paper and running tap water. Method: Caution: do not put the charged rod near anyone's face or eyes. 1Blow into the balloon and tie off the end when it is inflated with air. Rub the balloon with a piece of wool and release it near a wall. Observe what happens. 1Rub the balloon over a friend's hair and observe what happens. 2Take the charged balloon near small pieces of paper and observe what happens 4Take the charged balloon near running tap water and observe what happens. 5Repeat the above steps with a perspex rod rubbed with wool. Results: Record your results in the table—put a tick if it is attracted. Objects tested Wall Paper Hair Water Charged balloon Charged perspex rod 21 Discussion: 1. Which objects did a charged balloon attract? ___________________________________________________________________________ ___________________________________________________________________________ 2. Why did the balloon stick to the wall? ___________________________________________________________________________ ___________________________________________________________________________ 3. What happened when a charged perspex rod was taken near paper, hair and water? ___________________________________________________________________________ ___________________________________________________________________________ Conclusion: How did you create static electricity in this experiment? ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ Static electricity is produced by friction when materials are rubbed together. The study of static electricity is called electrostatics. Types of charges All matter is made up of small particles called atoms. Atoms are made of smaller particles called electrons, neutrons and protons. Protons and neutrons are found in the nucleus (centre) of the atom. Electrons are smaller in size and move around the nucleus at high speed. •Electrons have negative charge. •Protons have positive charge. •Neutrons have no charge. Neutral atoms have equal numbers of electrons and protons. Rubbing can tear electrons from certain atoms and they become positively charged. Other atoms gain electrons and become negatively charged. 22 Complete the following: Atoms are made of particles called ______________, neutrons and _____________ , Protons and ___________ are found in the ___________ of the atom. _______________ are ______________ in size and move around the _____________ at high speed. Electrons have ___________ charge, protons have ______________ charge and neutrons have ___________ charge. A charged object has an ___________ force __________ around it and other objects will be attracted or ______________. Electrical Electrons No Field Negative Protons Neutrons Nucleus Smaller Nucleus Positive repelled Electrons Question 1. Look at the pictures below. For each picture, complete the two sentences to describe the forces that are occurring. The words in the box below will help you complete the first sentence for each picture. friction gravity buoyant force (upthrust) mechanical The type of force is ____________________ . It is acting between the ____________________ and the ____________________ . The type of force is ____________________ . It is acting between the ____________________ and the ____________________ . The type of force is ____________________ . It is acting between the ____________________ and the ____________________ . The type of force is ____________________ . It is acting between the ____________________ and the ____________________ . 2. Draw arrows to show the direction of the forces acting in each of the pictures above. Label each arrow with the name of the force. 3. Choose words from the box to complete the sentences. 23 energy build up pull magnet start energy stopped attract  repel Force is the general name for a push, a ____________________ or a twist. Forces can ____________________ , stop or change the direction of an object. Forces give ____________________ to objects. Motion cannot be started, altered or ____________________ except by a force. Electricity is ____________________ that results from the movement of electrons. When electrons gather together in one place a ____________________ of static electricity occurs. A ____________________ is an object that is able to attract magnetic material. Like poles ____________________ and opposite poles ____________________ . 4. Choose a word from the box to complete the sentences below. You may use a word more than once. poles north magnetic metals repel lines magnetism Magnets point to the ____________________ pole if you hang them from a string. Heating a magnet destroys its ____________________. Planes and large ships use ____________________ compasses for navigation. A magnetometer is a sensitive magnet that finds ____________________ underground. ____________________ resonance imaging (MRI) is used to find out what is wrong with sick people. Like poles ____________________ and unlike (different) poles attract. The magnetic north pole of the Earth attracts the ____________________ pole of a compass. The magnetic field of a magnet is strongest near the ____________________ of a magnet. Magnetic field ____________________ can be used to represent a magnetic field. 24 2 Add the following labels in the correct places on the diagram below. geographic north pole geographic south pole magnetic north pole magnetic south pole north-seeking pole of magnet south-seeking pole of magnet 3Cross out the wrong word in each sentence. a. North and south poles attract/repel. b. Two south poles attract/repel. c. Two north poles attract/repel. 4You are given three similar painted metal rods, one made of copper, one of soft iron and one a permanent magnet. Describe how you could distinguish between the three rods without using any other equipment. (Note: copper cannot be magnetised.) ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 25 Concept: The gravitational attraction between two objects depends on their masses. The bigger the mass, the stronger the gravitational Force. Everything made of matter is affected by the pull of gravity. All matter on or near the Earth is attracted to the Earth. In fact, all bits of matter attract each other. Sir Isaac Newton discovered this in the seventeenth century. Gravitational forces exist between objects even when they are not touching. For example, there is a gravitational force between the Earth and the moon. This keeps the moon in place. Similarly, a gravitational force keeps satellites in orbit around the Earth. The Earth itself is kept in orbit around the sun by a gravitational force. So are all the other planets. Concept: Mass is the quantity of matter in an object. It is measured in grams or kilograms. Weight is a force — measured with a spring balance. It is the downward force of gravity. Because it is a force, weight is measured in newtons (N). The scales of weighing machines are usually marked in mass units (kilograms). This is why most people think mass and weight are the same, even though they aren't. When you weigh yourself, you are measuring the pull of gravity on you. And this is a force, not a mass. The moon has less mass than the Earth. So the moon would not attract you as strongly as the Earth does. This is why gravity is less on the moon than it is on Earth. Your mass does not change, but your weight does You can jump higher on the moon, and you don't come down as quickly as you would on Earth. Question 1. Match these weights with the correct object. 1N 50 N 450 N 10 N a 5 litre can of petrol the Guinness Book of Records an apple you Mass and weight are not the same. 26 2. Are the following statements true or false? Statement Mass and weight are the same. Weight depends on gravity. Mass depends on gravity. Objects are light when gravity is weak An astronaut has the same mass on the moon as on Earth. An astronaut weighs the same on the moon as on Earth. The moon's gravity is stronger than the Earth's gravity. Gravity only affects heavy things. 3. Look at the figure below. Circle the correct word to complete these sentences in your notebook. True/False a. The force of gravity is a (push/pull). b. A force pulls the spring (up/down). c. The heavier the object, the (less/greater) the force. d. The stronger the force, the (more/less) the spring stretches. e. A 10 N weight is a (stronger/weaker) force than a 20 N weight. f. A 20 N force stretches the spring (twice as much/half as much) as a 10 N force. 27 Find each of the following words. ATTRACT POSITIVE CHARGE CONTACT REPEL MASS PROTON ELECTROMAGNET FORCE FRICTION PUSH NEGATIVE SOUTH MAGNET WEIGHT ELECTROSTATIC NORTH ELECTRON NEWTON TENSION SURFACE BUOYANCY GRAVITY PULL N T I N C I N I L R C P E E A I S A E H N N N O R T C E L E E O U N O N M N H T S L N P O H I C R H F O G A O Y C N A Y O U B R F A R R N A G H H E F C E T N C A E I T T C M N O T O R P E E R C L C H G M C O E A R M S N G C E O T E I O E T R T C T H S A I N T I T B G N O T T E A T I T T A I O L R O U I T R C I T O I R T O N A T L C V T C P E V N V P T P H W U A I A A E E P L G E E R C E L E P E R V E N N T E G N A N N N N T O I S O A F W R R C C C N N E C T S O C O E A E T H T G C E T I S S U E I V C G M L E I B E S E H N T G I O N C A L N P T O Y Y L A H T N T T T S T P T P M R A O T Y T P H E V S G U E O C P U S H A A E E A S R A L N R V R O C C C A A F N L O S L G E L E C T R O S T A T I C T E V H R A T M A T T G E L I T T 28