PRESSURE. Prepared by: Aziah Yahaya

Transcription

1 PET R O SA INS Teacher Activity No S ucke r Pressure Are You A suggish Snail Or A Turbon Cold Station Fruit Conductors How Elevator Save Energy Ring The Alarm! Station Electricity WaterCraft Teacher fellowship program 2006/COL/teacher activity

2 PRESSURE Introduction These activities introduce the concept of atmospheric pressure and its application in our daily life. At the end of the activities, students should be able to understand principles of basic pressure and how a vacuum cleaner works. 1. NO SUCKER What do we need? An empty plastic bottle Drinking water 1 Knife/blade Some plasticine What do we do? 1. Fill the plastic bottle with some drinking water. 2. Using a knife/blade, poke a hole in the bottle cap big enough for a straw. x x

3 3. Put the straw into the water through the hole in the lid and seal up the space around the straw with some plasticine. 4. Try to suck through the straw. Did the water go into your mouth? What s happening? Water could not come through the straw. When you drink from an open glass of water, air pressure allows the water to travel up the straw. When you reduce the pressure inside your mouth (by sucking on the straw), the surrounding air pressure pushes down on the water and forces the liquid up the straw. When the bottle cap is sealed, there is no air pressure to help push the water up the straw to go into your mouth.

4 2. Now cut a slit down one side of the bottom third of the bottle. This will allow you to slide it through the top part of the bottle so that it can act as a piston. 3. Cut a 6 x 3 strip of paper and fold it in half lengthwise for extra strength. Tape this strip to the opened part of the bottom third of the bottle to make a handle for your piston. 4. For the top part of the bottle, cut a inch hole about 1 inches below the neck. This hole will lead to the filter bag. 5. Make a filter bag for your vacuum with a 6 x 4 piece of tissue paper. Fold the paper rectangle in half and tape the sides to make a bag. Tape this over the hole you made near the neck of the bottle. 6. Tape one end of a thread to a ping-pong ball. Put the ball inside the top part of the bottle. Feed the free end of the thread through the mouth of the bottle, and tape it to the outside of the bottle so the ping-pong ball hangs just slightly below the neck.

5 2. A VACUUM CLEANER Introduction A vacuum cleaner is able to suck dirt off carpet because high pressure air from the outside flows towards the low pressure air inside. The higher pressure air outside the vacuum is sucked in to replace the lower pressure air, bringing dirt and dust with it to be caught in the filter bag. What do we need? 1 A4 paper Some thread Adhesive tape 1 ping-pong ball One 1.5L plastic soda bottle Some tissue paper 1 razor Knife/blade What do we do? 1. Cut off the soda bottle about of the way up from its base.

6 7. Push the bottom cut-off part of the bottle into the upper part of bottle, and then pull it back sharply. What s happening? Pulling the piston back decreases the air pressure inside the bottle, as there is bigger space for the same amount of air (volume of space increases). The lower pressure air inside the bottle creates suction, pulling in higher pressure air from outside in through the mouth of the bottle. As you push the piston, the air is compressed and pressure increases in the vacuum, so air flows back out of the bottle. The ping-pong ball works as a valve. The table below shows how the atmospheric pressure varies with altitude. Fraction 1 atm Avg. altitude in meters 1 0 ½ / / / / / / The Earth s atmospheric pressure varies broadly and these changes are important in meteorology. The recorded atmospheric pressure during hurricane Wilma on 19 th October 2005 was 33.2 kpa (882mbar or 66.8 cmhg). Reference: (1/12/2006, 10:10 AM) Curriculum Specifications Link Physics Form 4: Pressure (Atmospheric pressure)

7 Sluggish Snail or charged Cheetah? Prepared by: Chin Chee Keong Introduction How fast is your reaction? What do we need? Two people A meter ruler A calculator What do we do? 1. Hold the metre ruler with its zero reading pointing downwards. 2. Person A positions his/her thumb and index fingers 8cm apart at chest level at a comfortable distance from the body. 3. Person B holds the metre ruler inbetween Person A s fingers. 3. Person B drops the ruler straight down suddenly. 4. Person A grabs the ruler upon its release and holds it. 5. Take the reading where the subject grabbed the ruler. 6. Repeat steps 1 to 5 thrice for an average reading. 7. Convert the distance into milliseconds using this formula: = d t Tabulate all data and look for effects on the reflex time of subject of a different age and sex. e.g. Prepared by: Chin Chee Keong

8 Age range (years) Reaction time (millisecond) or Sex Female Male Reaction time (millisecond) or Physical activity Before push-ups After 20 push-ups Reaction time (millisecond) What s happening? Nervous responses to environmental stimuli are fast and only takes a small fraction of a second to be completedthe body must react quickly to avoid painful or dangerous stimuli. Various factors affect our reaction time. Curriculum Specifications Link: Science Form 2: The World Through Our Senses Biology Form 5: Body Coordination System Prepared by: Chin Chee Keong

9 COLD STATION Prepared by: Chin Chee Keong 1. RUBBER BLUBBER GLOVES Introduction How do sea mammals survive in the cold sea water? Let s find out! What do we need? A pair of rubber gloves Masking tape A stopwatch A pair of plastic gloves A thermometer Some Vaseline or shortening A container half-filled with ice water What do we do? 1. Take its temperature of the ice water in the container. 2. Dip your hand into the ice water and start the stopwatch. How long can you keep it there before it gets too cold for you? 3. Take your hand out of the ice water and let it warm to your normal body temperature. Prepared by: Chin Chee Keong

10 4. Now put on rubber gloves on both hands. Carefully insert the thermometer into each glove. 5. Apply a thick layer of shortening over the rubber gloves of your right hand. 6. Put on plastic gloves over both hands and secure it with masking tape. 7. Dip both hands into the container of ice water. 8. Start the stopwatch. How long can you keep your hands in there? 9. Remove your hands after 5 minutes. Which hand feels cooler? 10. Check the reading of the temperature. Which one shows a lower temperature? What s happening? Sea mammals like whales and seals have a thick layer of fat underneath their skin called blubber. The blubber keeps them warm. The layer of shortening on your right hand glove helps to reduce loss of heat from your hand to the ice water. Prepared by: Chin Chee Keong

11 2. ICY FINGERS Introduction How does a cold environment affect our sense of touch? What do we need? 5 toothpicks A thumbtack A stopwatch A small plate A plastic container with lid A container of ice cubes What do we do? 1. Break a toothpick into 3 smaller pieces. Do this with all the 5 toothpicks. 2. Use a thumbtack to make one small hole on the lid of the plastic container. The small hole must be big enough for the toothpicks to pass through. Prepared by: Chin Chee Keong

12 3. Start the stopwatch as you begin to pick up a small toothpick from the plate and insert it into the plastic container through the small hole. How long did you take to finish inserting all the 15 pieces of toothpicks? 4. Now dip the same hand into a container of ice for 30 seconds. Dry your hand, pick up the broken toothpicks and insert them into the plastic container in the same manner. How long did you take to finish inserting all the 15 peices? What s happening? Our hand feels cold being in the container of ice cubes. When our body is cold, there will be less blood flow to the skin. The skin becomes less sensitive, which dulls the sense of touch. That is why it is harder to pick up the toothpicks. Curriculum Specifications Link Science Form 1: Heat Science Form 2: Sensory Organs Physics Form 4: Heat Prepared by: Chin Chee Keong

13 Fruit Conductors Prepared by: Bebe Zarjan bt Mirbas Khan Introduction Can fruits become electrical conductors? What do we need? What do we do? 1. Connect one end of the black wire to a battery and the other end to a LED indicator. 2. Connect the red wire to the other battery terminal and its other end to a paper clip. 3. Using the metal wire, attach a paper clip to one of its ends. 4. Connect the other end of each black and red wire to a LED indicator. 5. Insert the tip of both paper clips into the fruit right down to the fleshy part and observe what happens. Prepared by: Bebe Zarjan bt Mirbas Khan

14 What s happening? The liquid in the fruits will allow the current to pass through and the LED indicator will light up when the circuit is complete. The LED indicator will be brighter if the fruit has more acid in it. Curriculum Specifications Link Science Year 4: Investigating Materials - Conductor or Insulator? Science Year 3: Electricity WATCH OUT! Do not hold the paper clips at the end of the wires with wet hands as you might get electrocuted. Prepared by: Bebe Zarjan bt Mirbas Khan

15 Introduction HOW AN ELEVATOR SAVES ENERGY Prepared by: Rohaizad Mohamed Akhir A. How Elevators Save Energy (Set Induction) Can an elevator be operated on the same amount of electricity as that used to light up a bulb? Yes,it can be done as it performs this energy-saving feat by using a system of counterweights. B. The Magic of Pulleys Using the same pulley setup as the elevator model we can explore the magic of pulleys. In this activity, we are going to see the difference between fixed and moveable pulleys, and how moveable pulleys reduce the amount of force needed to lift heavy things. What do we need? A. How an Elevator Saves Energy (Set Induction) B. The Magic of Pulleys Prepared by: Rohaizad Mohamed Akhir

16 What do we do? A. How an Elevator Saves Energy 1. Using screws, attach pulleys and spools to the wood as in picture A. 2. Make a detachable elevator cab model using a magnet in a box. 3. Tape two bar magnets and hooks using masking tape (Picture B). Make another 5 sets of these counterweights. 4. Take 3 separate pieces of string; pull it through the pulleys and over the spools (Picture C). 5. For ease of dismantling, the string ends are connected to key rings and hooks. They will be used for both the elevator and pulley models. 6. Connect the strings to the elevator cab model and the counterweights, and adjust their lengths accordingly. 7. Add extra weight to the elevator by hooking on more magnets, and see how many magnets you need to balance the weight. Continue experimenting with different weights. 8. After each balancing, try lifting the cab up and down by moving the counterweights. Does the cab seems heavier, or remains light? 9. Compare this model system with a see-saw model. How are they similar? B. The Magic of Pulleys 1. Disconnect the elevator cab from the set. 2. Attach the fixed pulley system on the left side of the board, and see how many weights or magnets you need to pull up the load. 3. Make a moveable pulley system by pulling a string through the pulley, and attach a hook at each end of the string (Picture D). 4. Attach the moveable pulley system on the right hand side of the set (Picture E). 5. See how many weights you need to pull up the load. 6. Is there any difference between the fixed and moveable pulley systems? Prepared by: Rohaizad Mohamed Akhir

17 Picture A Picture B Picture C Picture D Picture E What s happening? A. How an Elevator Saves Energy An elevator runs on minimal electricity as it uses the pulley system and the appropriate counterweight (represented by the magnets). This amount of electricity can be as little as that used to light up a bulb! It is exactly the same principle as in a see-saw (a lever), where you need minimum amount of energy to move either side of the lever when it is perfectly balanced. When you step into a lift cab, it will experience an additional weight, and balances this by adding the appropriate amount of counterweight. This reduces the energy needed to move the carriage up and down the shaft. Prepared by: Rohaizad Mohamed Akhir

18 B. The Magic of Pulleys Pulleys are grooved wheels that are useful in assisting us in lifting heavy things. A fixed pulley system changes the direction of the force and makes it more comfortable for us to move a load, usually from raising a load to pulling it down. Moveable pulley system changes the amount of force needed. However we still need to perform the same amount of work as the distance of the pulling has increased. Curriculum Specifications Link Primary Year 4: Investigating the Earth and the Universe - Gravity Primary Year 6: Investigating Technology - Simple Machines (pulley, lever) Prepared by: Rohaizad Mohamed Akhir

19 RING THE ALARM! Prepared by: Bebe Zarjan bt Mirbas Khan Introduction Can you burglar - proof your belongings? What do we need? A school bag A 9V battery 20 cm of metal wire 2 bar magnet A buzzer 2 bar magnet A big paper clip Aluminium Foil Connecting wires (20cm black, 20mcm red) 4 Crocodile Clips A mounting board (size fits the bottom of school bag) What do we do? 1. Connect the buzzer, wires, battery, magnets and crocodile clips as shown in the schematic diagram of the circuit. 2. Place the circuit at the bottom of a school bag. Arrange the wires so that the two foil ends are near to each other but do not complete the circuit. 3. Ask a friend to carry the bag and observe what happens. Prepared by: Bebe Zarjan bt Mirbas Khan

20 Buzzer Paper Clip Aluminium Foil Magnet What s happening? Any movement of the bag will cause the magnet to attract the paper clip. This will complete the circuit and the buzzer will start to ring. A circuit is complete if there is current flowing through it. Curriculum Specifications Link Science Year 2: The Magic of Batteries Science Year 3: Electricity Science Year 4: Investigating Force and Energy Ring...ring... Ring...ring... Noise!! Prepared by: Bebe Zarjan bt Mirbas Khan

21 3.An Electroscope What do we need? 1 polystyrene cup 1 balloon Thread (8 ) 1 Drinking straw Aluminium foil (3*3) 1 wooden ruler Masking tape 1 aluminium pie pan 1 polystyrene plate Some plasticine What do I do? 1. Make two holes on opposite sides near the base of a polystyrene cup. A good way to do this is by pushing a sharp pencil, chopstick or skewer through the cup. 2. Push a plastic straw through the holes in the cup.

22 3. Stick four little balls of plasticine to the rim of the cup, each about half-inch in diameter. 4. Turn the cup upside down and stick it to the bottom of the aluminium pie pan using some plasticine. Make sure that the cup is right at the edge of the pan s base so that the straw sticks out over the edge of the pan. 5. Cut a piece of thread about 8 inches long and tie a few knots in one end of the thread. 6. Cut a one inch square of aluminium foil. Use it to make a ball around the knots in the thread. The ball should be about the size of a marble. It should be just tight enough so it doesn t fall off the thread.

23 7. Tape the other end of the thread to the tip of the straw so that the ball of foil hangs straight down from the straw, right next to the edge of the pan. 8. Tape the straw to the cup so it doesn t move around when you use the electroscope. 9. To test the electroscope, create some static electricity. You can do this by rubbing a blown balloon on a polystyrene plate. 10. Now that you have created some static electricity, place the electroscope on top of the polystyrene plate. 11. Using a wooden ruler, measure the distance between the foil ball and the pan. The more the charge, the more the distance. Be careful not to touch the ball or the edge of the plate with the ruler when you measure. 12. Now touch the ball with your finger. What happens? 13. Try charging different objects with static electricity and testing them with the electroscope. What s happening? Rubbing the polystyrene plate charges it. This means there is a build-up of electrons on either the balloon or the plate. Even though the plate is charged, the electrons do not move as polystyrene is not a conductor. Electrons move easily through metal, so when you put the aluminium pie pan onto the charged polystyrene plate, the electrons travel into the pan. The added negative charges on the pan repel the negative charges on the foil ball as shown. Curriculum Specifications Link Science Form 3: Electricity

24 2.Glowing Glue What do we need? A pair of scissors A dark room A self adhesive rectangular envelop What do we do? 1. Seal the envelope, as though you were closing it. 2. Cut the top part of the envelope where the adhesive is (the only bit you want is the sealed part-where the strip is stuck to the envelope). Discard the rest of the envelope. 3. Find a dark room and allow your eyes to adjust to the darkness. 4. Predict what you think will happen when you slowly pull the two strips of paper apart. 5. Observe closely. 6. Explain what you just saw.

25 What s happening? A faint blue glow will appear from the place where the two strips are being pulled apart. The glue being pulled apart produces tiny sparks between the pieces of paper. All matter contains particles with an electric charge. Normally the number of positive and negative charges is the same, so they cancel each other out. When you pull two strips of an envelope apart, some of the glue stays stuck to one side and some stays stuck to the other side. As the glue divides, the negatively charged particles (electrons) do not split evenly. Either one of the strips would have more electrons. This build-up of negative charge is enough to make a spark jump the tiny gap between the strips. This spark makes nitrogen molecules in the air glow blue, producing the light you can see.

26 Static Electricity Introduction Static electricity is the build-up of electrical charges in an object. It can be created by rubbing one object against another object. The rubbing produces friction which releases negative charges called electrons that accumulate to produce a static charge. 1. FLAKE(Y) MAGIC What do we need? Corn Flakes Adhesive tape Some cereal flakes 1 shallow paper bowl Plastic wrap (at least 40cm 40cm) What do we do? 1. Fill half of the bowl with cereal flakes. 2. Cover the bowl with a piece of plastic wrap. Secure the plastic wrap with tape, making sure that the plastic is pulled taut. 3. Rub your knuckles eight to ten times across the plastic wrap that covers the flakes. 4. Observe what happens to the cereal flakes in the bowl.

27 What s happening? The flakes will begin to jump up and cling to the underside of the plastic wrap as if holding onto it with invisible, strong arms. As you rub your knuckles across the plastic wrap, millions of electrons leave your hand and pile up on the surface of the wrap. This creates a strong negatively charged surface. Since like charges repel, the negatively charged plastic wrap pushes away electrons to the bottom of the bowl. The plastic wrap surface is now positively charged. Since unlike charges attract, the positively charged flakes move toward and cling to the already negatively charged plastic wrap.

28 Introduction Pupils learn about transformations of energy, from one form to another. Pupils also understand that inert objects also contain energy, as in this case an inert column of water and an inert (stretched) elastic material. What do we need? MULTI-PROPULSION WATERCRAFT Prepared by: Rohaizad Mohamed Akhir 1 balloon 1 paper cup 2 bendy straws Some rubber bands A Sharp Pencil Some plasticine 1 Kebab stick Masking tape A paper puncher The cover of a thin plastic food container A Cutter What Do We Do? 1. Cut two pieces of Styrofoam to the shape shown in the template. Glue both pieces together back to back. 2. Make a shallow hole on the upper layer to hold the cup (represented by dotted lines in the template). 3. Using a sharp pencil, make holes for straws in the middle and front parts of the Styrofoam (Diagram A). Teacher fellowship program 2006/COL/Mini Show Prepared by: Rohaizad Mohamed Akhir

29 IMPORTANT: The centre hole has to be in a perfectly middle position; otherwise the watercraft will be imbalanced. 4. Push a straw through each hole and point the bottom part of the straws to the back of the boat. Secure with masking tape. (Diagram B). 5. Attach a balloon to the front straw and secure it in place with a rubber band. 6. Take the paper cup and make a hole at the bottom. Push the middle straw through the hole, and secure it in place with plasticine (Diagram C). 7. Break a kebab stick into two equal lengths. Push it through the back part of the Styrofoam boat (Diagram D). 8. Cut a small square out of the plastic cover. Using a paper puncher, make a hole on the two opposite sides of the square as shown below. Teacher fellowship program 2006/COL/Mini Show Prepared by: Rohaizad Mohamed Akhir

30 9. Pass two rubber bands through the holes in the square and loop them over the kebab sticks (Diagram E). a. For elastic band propulsion: wind up the rubber band. Release it and see it unwinds and turn the plastic square. b. For water jet propulsion: fill up the cup with water and see how the boat moves as the cup empties. c. For air jet propulsion: blow up the balloon (by blowing through the straw), release the boat and see how it moves. *Reminder: Ensure that the middle straw is submerged in water when the boat is released. What s happening? When you wind up the rubber band, it stretches and stores potential energy. As you let it go, it returns to its original shape and in doing so releases kinetic energy. When you put water into the cup, it has potential energy, and as gravity pulls it out through the straw, it will gain kinetic energy. The resulted water jet propels the boat forward. Blowing air into the balloon will stretch the balloon s elastic wall, and it gains potential energy. As you release the air, potential energy is transformed into kinetic energy of moving air, and this moves the boat forward. Curriculum Specifications Link Primary level Year 4: Investigating The Earth and the Universe: Gravity Primary level Year 4: Investigating the Material World (Elasticity) Primary level Year 5: Investigating the Physical World (Forms of Energy) Teacher fellowship program 2006/COL/Mini Show Prepared by: Rohaizad Mohamed Akhir