job: Chris Fawkes, BBC Weather forecaster (meteorologist)

Transcription

1 1/10 theme: nature job: Chris Fawkes, BBC Weather forecaster (meteoroogist) activity outine Using the context of a weather forecaster being abe to predict wind speed and direction, pupis use knowedge of isobars to work out the wind direction on a weather map. They then investigate how a barometer works, pressure, force and surface area. They conduct a series of experiments using U-tubes, syringe pistons and force meters. You wi need one or two essons, incuding an optiona teacher demonstration. The activities for How does a barometer work shoud be achievabe by a pupis in one esson. The activity to investigate pressure, force and area is more invoved it may be better suited to more abe pupis (with hep from the teacher) in a separate esson. It is suggested that pupis work in sma groups (2-3). The pupi sheet provides an introduction (which provides information about how to work out wind direction on a weather map), a weather map and step-by-step instructions for each of these procedures, as we as a resuts tabe to compete. Teacher notes overview 1 Curricuum 2 The 3 The inks: where this activity can fit with the 2008 KS3 Programme of Study and Scottish 5-14 Science Curricuum. Video: providing a synopsis of the video content and ideas for viewing. Practica: incuding Equipment ists, Heath and safety notes, a Possibe approach (a comprehensive, suggested way of panning the essons) and an Underying science section (providing detaied information about the various scientific principes invoved). 4 Possibe 5 Associated extensions: suggestions for other practica activities using the video, or extending the suggested activity. jobs: guidance on how to deiver a penary activity (or, if you wish, a stand-aone activity) focusing on the video interviewee, incuding a photo of the interviewee to pace at the centre of a spider diagram.

2 2/10 curricuum inks This esson can be used to hep teach part of the 2008 Key Stage 3 Programme of Study (Engand and Waes): Range and Content: 3.1b Attainment Targets: AT1, AT4 Key Concepts: 1.1a, 1.1b, 1.3* Key Processes: 2.1a, 2.1c, 2.2a, 2.3a Curricuum Opportunities: 4a, c, h This esson can be used to hep teach part of the Scottish 5-14 Science Curricuum: Main curricuar inks E&F3 Forces and their effects Attainment Targets Knowedge & understanding: Leve E Describe the reationship between force, pressure and area Investigating skis: Leve D Make an appropriate series of accurate measurements Draw concusions consistent with findings * if Torricei is discussed

3 3/10 the video Synopsis of the video Among other things, Chris makes these interesting points: The MetOffice uses a super computer to try to mode the atmosphere; even though it s one of the most powerfu computers in the word, it sti has to simpify the atmosphere because it s extremey compex. Weather forecasters are sti needed because they can ook at the computer s mode, and compare this with human readings from around the country, thus spotting computer errors and tweaking the mode. Weather presenters stand in front of a bank bue screen they can t see the maps that we see when we watch on the teevision. You need an exceent knowedge of physics to become a meteoroogist. Watching the video There are a number of things you might do before showing the video to your cass. 1 Preview the video and write a few quick-fire questions. Then you can te your cass that they wi be tested on their observation when it s finished. This is an exceent way of encouraging them to pay attention! 2 Ask 3 Ask 4 Ask pupis to watch the video through once. Then ask them to generate one question that coud be answered from the video and one question they woud ike to ask but the video did not answer. These questions are then exchanged with another pupi and the video is watched a second time. This gives pupis an opportunity to focus on something they may have missed first time, and provides a basis for discussion on what was earnt from the video, and what additiona information is needed. pupis what sort of person might become a weather forecaster. Does anyone in the cass think they d ike to work in meteoroogy? When the video has been watched, ask the questions again. Has anyone changed their mind/opinions? pupis to spot the science in the cip.

4 4/10 the practica Equipment (per group of 2 or 3 pupis) U tube (or manometer) sma syringe attached to bung to fit U tube (attachment must be airtight) sma trough (or arge beaker) test tube pastic tube about 1m ong cip to sea end of tube pastic tube 3 to 4m ong (optiona) access to dye soution to coour the water 3 syringes of different sizes, arger than the sma one above short fexibe tubing to connect syringes access to 50% detergent soution or simiar, to ubricate syringe pistons 3 camps + 2 stands 2 compression forcemeters step adder or access to a staircase, if using the onger tube Note: Try this experiment in advance to match forcemeter range to syringes used. The force required depends on how easiy the pistons side. The pistons in new syringes are aready ubricated; used ones may need ubricating to minimise friction. For water barometer demonstration (extension activity) pastic tube at east 10.5m ong + seaing cip 10m of strong string or cord 15m tape measure

5 5/10 Possibe approach Ideay, the esson shoud take pace in a ab with a mercury barometer on the wa. (Warning: Do not attempt to remove the barometer or carry it esewhere, since this coud easiy break the tube, resuting in mercury spiage.) Introduce the concept of air pressure and its importance in potting weather maps. [Note: at the top of the student sheet there is a weather map; students are asked, What is the wind direction across Ireand?. The answer is North West.] Discuss how the pressure is measured. Expain that the experiments show how a barometer works. Pupis carry out the first set of experiments to show how air pressure can support a coumn of water. It is suggested that they work in groups of two or three. Discuss the resuts, emphasising the importance of forces in baance. Ensure that pupis understand the terms force, weight and pressure and their reationships. If possibe, with pupis hep, demonstrate the water barometer extension activity, to show that air pressure can support a coumn of water some 10.3m high. Theoreticay, they coud suck up a drink through a 10 metre straw, but not much higher. Ask why not. Lead discussion into expanation that suction is an iusion. The drink is being pushed up by air pressure, not being sucked up. Introduce the mercury barometer, and its diagram. Point out the anaogy with their water-in-atrough experiment. Ask why it is ess than 1 m high, rather than over 10m. Given that the density of mercury is 13.6 times greater than that of water, get them to cacuate the height of mercury that exerts the same pressure as 10.3m of water. (Ans: = 0.757m; i.e. about 75.7cm) Expain what we mean by pressure is force per unit area incuding units. Note: The SI unit is the Pasca (1 Pa = 1 N m -2 ), but they wi use N cm -2 for convenience in their experiment. Knowing that pressure is force per unit area, pupis now investigate whether the area of mercury exposed to air pressure affects the reading. If so how? If not why not? They use a compression forcemeter to appy a known force to a syringe piston of known area. Hence they can cacuate the appied pressure. This pressure exerts a force on the second syringe piston of different area. The resuting force is measured with a second forcemeter. It is important that the pistons side easiy in the syringe barres to minimise friction osses. Lubrication with 50% detergent soution may be needed. Pupis try at east two, preferaby three, syringes with pistons of different surface areas, taking readings for three appied forces for each syringe. Aowing for experimenta uncertainty and inaccuracies, their resuts shoud indicate that statements 1, 4 and 5 in their worksheet are correct. Discuss these concusions and the reasons why they are true. Lead the discussions into expaining why the size of reservoir and width of the mercury coumn in a barometer do not affect the pressure readings.

6 6/10 Underying science: Basic principes Readings of atmospheric pressure are fundamenta to weather forecasting. By potting arge numbers of readings, a pressure map is buit up showing regions of high and ow pressure. Isobars on weather maps are anaogous to contours on physica maps they join paces with the same atmospheric pressure. Like any other fuid, air fows from where there is a ot (high pressure) to where there is ess (ow pressure). High pressure forces air outwards towards the surrounding ow pressure. Winds aways bow from high to ow is an easy rhyme for pupis to remember. The Earth s rotation causes the air/wind to be defected to the right in the Northern hemisphere (and to the eft in the Southern). Going into detai of the Coriois force is probaby not advisabe at this eve! (athough Chris does mention it in the video). The weight of the atmosphere (that is the force of gravity puing the gas down) pushes on a surfaces. Air pressure is the force pushing on each square metre (or square centimetre) of surface. Normay we don t notice this pressure because it is equay spread as in the first U tube experiment. Increasing the pressure on one side of the U tube causes an imbaance, which forces the water down on that side and up the other, unti the pressure caused by the weight of the extra water baances out the extra air pressure. If there is no air pressure on one side, the air pressure, without any extra, is sufficient to support a coumn of water. (Experiment part 2) [Air pressure wi support a water coumn over 10 metres high but don t mention this yet if the water barometer extension activity is to be performed.] A mercury barometer is ike the water-in-a-trough experiment a tube of mercury standing in a reservoir, which is encosed to avoid escape of poisonous mercury vapour. A sma hoe aows the changing atmospheric pressure to contact the mercury surface. In some types (e.g. Fortin barometer) the mercury is hed in a sma eather bag. Since mercury is much denser than water, a coumn of mercury is much heavier, so exerts a much higher pressure. Air pressure can ony support about a 76cm coumn.

7 7/10 possibe extensions 1 Water 2 Pressure 3 Air 4 Historica barometer This requires access to a window, or a stairwe, at east 10.5 m above ground eve, and a pastic tube at east 10.5 m ong. Competey fi the tube with cooured water, e.g. by graduay owering the cois into a bucket. Hoding the end under water, fod it over and camp firmy to sea the end, ensuring that no air is trapped. Send one or two pupis up to the window with the cord and tape measure. Lower down the string or cord, and attach it to the seaed end of the tube. Carefuy pu the tube upwards to window height, being carefu to keep the ower end under water. Observe the coumn of water. Lower the zero end of the tape measure. Hod zero at the bucket water eve, and read off the height of the water coumn. Depending on atmospheric pressure, it shoud be between 10 and 10.5m high. Ask what is above the water eve at the top of the tube, and where it came from. (A vacuum caused by water dropping to the maximum height that the air pressure can support.) cacuations Weather maps normay show pressure in miibars (mbar). Reate these to barometer readings in mm Hg and SI units (Pa = N m -2 ). Pupis use conversion factors to transate between units but make these purposefu e.g. a barometer reads Xmm Hg. How woud this be potted on a weather map in mbar? (Or vice versa.) pressure and atitude Air pressure decreases with height. Discuss why and how this affects barometer readings. Given time, this coud extend into mountaineering and passenger aircraft. Note: Readings coected for weather maps must be adjusted to their corresponding vaues at sea eve before potting. deveopment For PoS 1.3 (Cutura understanding) pupis coud research the invention and deveopment of the barometer by Torricei et a. Continued >

8 8/10 5 Aneroid barometers Most dia-type wa barometers, with which pupis may be famiiar, are aneroid. Show an exampe, or iustrations. This type contains a seaed, fexibe container, which expands and coapses sighty as the air pressure on it aters. This movement causes the pointer to rotate. Fig 1 Pointer Spinde Lever Vacuum chamber

9 9/10 associated jobs A STEM (Science, Technoogy, Engineering and Maths) education provides pupis with skis and knowedge that are usefu in a sorts of careers. The video demonstrates how Chris, a BBC weather forecaster, uses such skis on a daiy basis. Chris works with numerous peope some directy, some indirecty. Some use STEM skis, others don t. By exporing this network of associated jobs, pupis wi, hopefuy, begin to see that even those in non-stem jobs wi find STEM skis usefu if they re communicating with someone in-stem, for exampe, some knowedge of their work wi be a great hep. Chris s spider diagram Try pacing Chris at the centre of a spider diagram (we ve provided a photo of Chris which you coud use see overeaf). You coud either create worksheets for pupis to compete themseves, or create the diagram on your whiteboard and then poo ideas. Ask pupis: who does Chris work with. They may draw information from the video he taks about weather observers, for exampe or they may come up with new ideas, such as the peope who programme and maintain the super computer, or weather forecasters for other organisations, such as the miitary or airports. Other, ess obvious, suggestions might incude the peope who design/ make/maintain the various measuring toos such as sateites, weather baoons, thermometers, barometers, anemometers, etc. Now ask pupis which of those jobs are ceary in-stem. Who ese might find some STEM skis hepfu? Why? You coud extend this by taking any one of the associated jobs and pacing them at the centre of a spider diagram, and starting the process again.

10 10/10 Chris Fawkes, BBC Weather forecaster (meteoroogist) Studying science and maths can transform your career options. Future Morph: become someone.