NIT 2 FORCE AND MOVEMENT FORCE MOVEMENT. Dynomometer. Upthrust. Electrical Force. Weight. Magnetic Force. Gravity. Resultant. Frictional Force.

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1 NIT 2 FORCE AND MOVEMENT Dynomometer is measured by Weight Upthrust Electrical Force Gravity means Magnetic Force FORCE Resultant Motion is opposite with in used for Frictional Force Work causes is done by Simple Machines MOVEMENT vectorial scalar Velocity Speed

2 2 Entry Activities Anything we throw upwards falls back down but none of the hunderds of satellites in space fall down. What is the reason for this? Discuss this with your friends and note your answers in your notebooks. Go over your answers after you finish the unit. When historical buildings were constructed many years ago there were no working machines like excavators or cranes.therefore how were the huge and heavy stones used in buildings moved or lifted up. Discuss this with your friends and note your answers in your notebooks. Go over your answers after you finish the unit. 20

3 Force and Movement FORCE AND MOVEMENT We get up in the morning open the bedroom door, slice bread put the book on our desk into our schoolbag and so on. We live our lives by performing many actions of this kind. Have you noticed that these activities are all pushing or pulling actions. We can see that a huge ship is pushed by its motors, or can observe how the wind moves the leaves around.in both cases, what we see is not the force, but it is the results brought about by force.in most general terms, force is the pushing or pulling action.we can understand the presence of force by seeing or feeling the results it brings about. There are two types of force;the one with a circular effect is the circular force and the one that forms a linear effect is the linear force. We open the lid of a jar by exerting circular force and we pull a weight by exerting linear force. 21

4 2 2.1 A - Forces in our Environment The Stone we throw upwards falls back down. We open our bedroom window by pushing it. Magnets attract (pull) metals like iron and nickel. We carry weights from one place to another either by pulling or by pushing them. If we let the stone in our hand go, it falls down. Is this caused by a force. Yes it is caused by the force of attraction. All the objects exert a force on one another, but the force exerted by small objects on one another is so small that it is negligible. However, the earth is so huge that, the force it exerts is large enongh to pull all the other objects to itself. This force is called the gravity. Water and air have the effect of lifting objects upwards, i.e. they have the buoyant force. Upthrust of Water Upthrust of Air ( Force of air resistance) Gravity Gravity Magnets attract some metals. There is rejection (pushing) or attraction (pulling) between magnets as well. This is called the magnetic force. There is a similar attractions in an atom, this is called the electrical force. Did You Know? The unit of force is named after Sir Isaac Newton, the scientist that found the Law of General Attaction. 22

5 Force and Movement 2.1 B - What is Force? When playing football, we send the ball to different directions, to our teammates or to the nets to score a goal. The ball gains different speeds according to the force we exert on it. It stops when the goal keeper catches it. When playing the rope pulling game, the team which pulls with a greater force, wins. If both teams pull with the same force, none of the teams wins as there will be no movement. The force used here is the force in our muscles. Different forces act on an object in different directions. If the object is stationary, then, all the opposite forces acting on it are balanced. In order for the object to move, the force in one direction must be greater than the force acting on it in the opposite direction. Force can move stationary objects, can stop moving objects or can change the direction of movement. 100 Newton 100 Newton Opposing forces are balanced, the object does not move. 20 Newton 100 Newton The right hand force is greater; =80N. The object moves to right with a force of 80N. 100 Newton 100 Newton 20 Newton 100 Newton 100 Newton The total force to the left is greater; (100+20) = 20N. The object moves to left with a force from of 20N Opposing forces (to the right and to the left) are balanced, but as there is another force from another direction, the object moves downwards. 100 Newton Did You Know? The billiard robot designed in Bristol University,England, can calculate the exact force that should be used to hit the balls. 23

6 2 2.1 C - How Do We Measure Force? We know that objects have mass and volume and that mass can be measured by using a scale.we now learned that one of the greatest forces acting on objects is the Granitational Force. Scientists prepared a scaled apparatus with a spring and decided that the amount of stretching of a 100gr object on this apparatus is equql to a force of 1 Newton.This apparatus is called a dynamometer. A dynomometer can be prepared in various forms.a manual scale with a spring is a dynomometer. The maximum amount of force that can be measured by laboratory dynomometers have a limited stretching capacity. Stretching capacity of the spring determines the amount of force that can be measured by that dynamometer. Gravitational Force The gravitational force acting on a 1 kg object on earth is approximately 9.81Newtons. Thus, we can calculate the weight of a 20 kg (mass) object is 20 x 9.81=196.2 Newtons. As can be seen from the given example weight is the gravitational force exerted on objects by earth. An astraunot on the moon has a smaller weight than he has on earth as the gravitational force on the moon is smaller than that on earth.in space, the astraunot has no weight as there is no gravitational force in space. Therefore; it can be stated that each object has a constant mass but its weight changes according to the gravitational force in different environment. Activity After studying the pictures above, draw the force(s) acting on objects, and state which one(s) are balanced. Did You Know? The gravitational force on the moon is 1/6 th of that on earth. 24

7 Force and Movement 2.2 A - Forces in Action I spent the day moving a stone out of our garden. I tied a rope around the stone and dragged it out. Finally, I did it. I got rid of the stone but I had a tiring work day. I wish the stone was closer to the fence,then I could move it outside much easily and would have a less tiring workday. However, the stone was very far from the fence and I had to put a lot of effort in order to move it outside. As given in the example above, scientists call the force applied times the distance moved by the object work. If the object does not move in the direction of force we apply, then we do not do any work. WORK = FORCE x DISTANCE Force: 100 Newton Joule Newton Meter Distance: 15 meter WORK = 100 x 15 = 1500 Joule If I was stronger, I could move the stone out much faster. Then I would not have to spend the whole day working. Scientists call the speed of work done power.power is the time taken to do the work. POWER = WORK TIME Joule Second Did You Know? Watt People evaluate the power spent for work. This is one of the fundamental principles of the Declaration of Human Rights The unit of power which was previously stated as horse power is named after James Watt the creator of steam machine. 25

8 2 2.3 A - Simple Machines Kyrenia Castle and Salamis ancient city are the examples of architecture that have remained from ancient times. Pyramids in Egypt are other examples of architecture from old times. How were these ancient buildings constructed at that time? How were these ancient buildings constructed at times when there were no modern machinery? Lenght of the slope is 800 meters Height is 100 meters Gained Force = = The largest pyramid is about 146 meters high. Large rocks used in building the pyramids were taken to a height of 146 meters by inclined planes or ramps. Lifting the rock directly upwards involves movement in a shorter distance, butit requires a much greater force. When it is carried by using an inclined plane, it has to be moved it is much smaller. A rock that would need thousands of men to be lifted can be brought to the same height by a few men. Using an inclined plane does not change the amount of work done, but the same weight is carried over a much longer distance. The larger distance in using an inclined plane, the smaller the force required. This is an example of a basic machine. Scientists name the basic machines that can change the type of force, the direction or the magnitude of force, as simple machines. Did You Know? Scientific ideas make your life easier. The Greek scientist Heron who lived in the 2nd century believed that even the most complex machines consists of 5 simple machines. 26

9 2.3 B - Inclined Planes In Our Environment Force and Movement Inclined Plane Inclined planes are the simplest machines used for many puposes. The front part of a ship Works as an inclined plane. It is because of this inclined planet hat the ship uplits water and moves along easily. Screw A screw, which has a wide variety of uses, holds two or more pieces together. Screws change the circular force into linear force. Altought a screw does not resemble an inclined plane, it Works like one. When a screw makes a complete turn, it moves a thead space. This is called a screw step. An ax is a machine that has two incline planes brought together. The sharp edge of the ax hits the tree bark, and with its gradually wideniry structure the tree into two. Activity Find 5 different inclined planes in your environment and state the use of each one of them. Did You Know? The ziper, invented in 1891 by an American called Whitcomb Judson, is a simple machine that Works with the help of three inclined planes. 27

10 2 2.3 C-We Are Lifting Heavy Weights With Small Forces Lever Levers are simple machines that consist of a rod and a support. According to the purpose of using the lever, the support can be placed any where below the rod. We use various levers in our everyday life. Fishing line, hammer scissors, balance(scale) are all examples of levers. Effort Load Pivot Load Distance Effort Distance Pulley We can change the direction and magnitude of a force by using a pulley. Elavators and cranes that do the lifting actions use pulleys. Pulleys are divided into three: Fixed pulleys, movable pulleys and pulley systems. Fixed pulley Movable pulley Force Pulley System Force Weight Force Weight Activity: Show the place of pivot, force and load points on each of the following levers. Weight Did You Know? In sailing ships, pulleys are used in folding and unfolding the sails faster and easier. 28

11 Force and Movement 2.3 D - Let Us Use the Rotational Force Wheel and Axle Wheel is one of the most important inventions. Vehicles move by the movement of an axle that is turned by wheels. The circular movement of the axle is changed into a linear movement by the wheel. As the cirumference of the wheel is much greater than that of the axle, the force exerted by the axle on the wheel is much greater than the force exerted by the wheel on the ground. Big area low force Little are high force The handle of a screwdriver is wider than its axle. Therefore, the screw can be rotated with a greater force. Screwdriver is a good example of a wheel and axle. Gear and Wheels Wheels with teeth or with belts are simple machines that change the magnitude and direction of force. Wheels that rotate are connected to each other by teeth or by a belt.as a result, the rotation of one wheel causes the rotation of the other. When the larger wheel makes 1 complete turn, the smaller wheel makes 2 or more rotations. Gear Wheels with teeth or with belts are used in bicycles. Chains, instead of belts, increase the strength of the connection. Wheel Activity By looking at the diagram aside, make a wheel with teeth. For this, you need a 1 cm thick potatoe slice, a cardboard box and 16 toothpicks. Did You Know? The smallest motor produced in the world was made by Toshiba and it is 1mmin width. 29

12 2 2.4 A-If There was no Friction! When we hit a ball, it moves, but it gradually slows down and stops. If we push a book on the table, it slows down and stops after a while. Any object we apply a force on slows down and stops after moving for a while. Why is this so? Force can cause the movement of a stationary object, can stop moving objects or learned the direction of movement. We learned this statement before. Then, it is a type of force which stops a moving object. Which one? This force is the friction force, As the frictional force opposes the movement of the object, it stops the object. Motion Frictional Force Force Applied Let us rub our hands together, what happens?our hands get warmer.if we continue to rub our hands, friction causes wear and our hands are hurt. Friction leads to loss of power, because some of the energy we use changes into heat energy due to friction, and it is lost. The frictional force affects the moving vehicles. Scientists have been working on a new vehicle design called aerodynamics in order to reduce friction caused by air. There are various ways of reducing friciton. If the rubbing surfaces are smooth or lubricated by grease or water friction between them is reduced. Friciton can also be reduced by replacing sliding movement into rolling movement. Place several marbles underneath yours book. Does it move easier? The frictional force affects the moving vehicles. Scientists have been working on a new vehicle design called aerodynamics in order to reduce friction caused by air. Soles are rough to prevent sweeping Friction has some uses. If there was no friction between our feet and ground, we would not be able to walk, we would slide and fall. That is why shoes have processes underneath, so that friction with the ground is increased. There is friction between a pencil and notebook. If there was no friction, writing would be impossible. It is almost impossible to write with a pencil on very smooth surfaces like glass that have very little friction. 30

13 Force and Movement 2.5 A - Let's Move When we look around, we notice that everything moves. Cars, bicycles, planes are continuously moving from one place to another. We know that the earth turns around the Sun and the moon turns around the earth. Briefly, everything in universe moves. Since everything moves in universe, we have to find a reference point for our own movement. Scientists call the movement from one place to another or changing one's position displacement. Displacement = Final position - Initial position Position Meters A B C D E According to the reference points given on the left, the displacement of a car moving from point B to D can be found by: Displacemet = Final position-initial position, Displacement = 6-2 = 4 meters. In this example the car that moved from point B to point D had a displacement of 4 meters. Here, the car's displacement is equal to the distance it covered. But sometimes, this is not the case. We know that displacement is the different between the two positions. Displacement is related to initial position, distance and direction. The sizes that involve the intial point, magnitude and direction are said to be vectorial. The distance is the amount of movement made by the car. Distance does not involve any sense of direction, so it is said to be scalar. School On the diagram given, two different ways are given to go from home to school. If the given way is taken: Green Road Displacement = 100 meters, Distance = 100 meters If the given way is taken: Red Road Displacement = 100 meters, Distance = = 140 meters Displacement is the same in both, because it means changing positions, However, the distance covered is different in each case. Home 100 meters 60 meters Did You Know? 80 meters The first car race took place in 1909 and the speed of the fastest car was 105 km/hour 31

14 2 2.5 B - Velocity and Speed The difference between velocity and speed is the fact that:velocity is vectorial, but speed is scalar. In other words, for finding the velocity of a moving object we use the vectorial displacement, but for finding its speed we use the scalar value of distance. Vectorial DISPLACEMENT VELOCITY = TIME SPEED = Scalar DISTANCE TIME Activity A Straight Road : 200 metre B Curving Road : 1500 metre We can move from point A to point B in 10 seconds when we use the straight road, and in50 seconds when we use the curving road.then, the velocity and speed for both roads can be calcualted as: Straight Road; Velocity = Displacement / Time Velocity = 200 / 10 = 20 m/sec Speed = Distance / Time Speed = 200 / 10 = 20 m / sec Curving Road; Velocity = Displacement / Time Velocity = 200 / 50 = 4 m/sec Speed = Distance / Time Speed = 1500 / 50 = 30 m / sec On a curving road displacement and distance covered are not the same, so velocity and speed are different. 32

15 Force and Movement TEST Match each of the following activities with the type of force used in performing that activity. a)carrying a table to another place by pulling it. b)opening the lid of a jar. c)cutting down a tree with an ax. d)lifting a weight by using a pulley. e)taking off a screw from a piece of wood by using a screwdriver. f)turning the pedals of a bicycle. Rotational Force Linear Force 2. State the type of force used on each of the following. 3. Look at the dynamometers below, complete the table given and answer the questions. I. A 0N 10 N 20 N II. B 0N 50 N 100 N III. 4. Which simple machines are found in each of the following objects? C 0N 1N 2N 3N Object Dynamometer Weight A B C a)which object is the heaviest? b)which dynamometer must be used in order to find the weight of an object of 1 Newton? 5. According to the references points given above which car is the fastest? Position A B C D E F G H I J K (Meters) Ferrari Mercedes Honda Moved from point D to J in 10 seconds Moved from point G to K in 20 seconds. Moved from point A to E in 50 seconds. 33

16 2 Multiple Intellegence Activities Add 5 more questions to the following and make up a survey of 10 questions. Ask these questions to at least 2 people from your families and friends. Draw the pictures of simple Machines below in the spaces provided. Q.1 : What do you think force means? Q.2 : In everyday life, for which activities do you use force? Q.3 : Give 2 examples of activities that use rotational force? Q.4 : What type of tools do you use to do work using less force? Q.5 : Give examples of simple machines? Inclined Plane Gear Wheel and Axle Pulley Lever Screw How would we live if there was no friction? We can do work using less force. Write a composition with a theme that is based on one of the facts given above. Write down problems that will need the use of the formula below to be solved. Work = Force x Distance Problem:... Solution: Power = Work / Time Problem:... Solution:

17 Force and Movement Multiple Intellegence Activities Symbolise each simple machine given below with a different colour and colour the boxes accordingly Screw Pulley Lever Inclined Plane Wheel and Axle Gear State the type of simple machine in each of the following by using your colour symbols. a) Ax b) Scissors c) Elevator d) Cart e) Screwdriver Write down a brief report on the negative effects of speeding in our lives. ( Title of the report ) ( Slogan) ( Information on the subject ) Apply the words below to one of your favourite songs or make up your own song. There are two types of force Rotational and Linear. Select and pick any simple machine you like. Screw, inclined plan Lever, pulley Do your work using less force Don't forget the wheel. State the type of simple machine you used during each time period given below. 07:00 to 10:00 : :00 to 13:00 : :00 to 15:00 : :00 to 18:00 : :00 to 21:00 :

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