2008_Y10_Exam

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Garfield graphics reproduced with kind permission from PAWS Inc.

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LOJ June 2008

Y10 Mock

ExamJune

2008

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Saving in kWh = 350 (old one) 225 (new one) = 125 kWh (1 mark)

Cost = 125 x 12p = 1500p (1 mark) = 15-00

ORwork out cost of running each one: old one = 350 x 12p = 42- 00;

new one 27-00 saving = 42-00 - 27-00 = 15-00

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This is another maths/economics problem NOT physics sorry guys it is the

way the subject is going they think it makes it more relevant!You save 15 per year and they say the payback time is 12 years that meansit costs 15 x 12 = 180

When it is reduced the payback time is 9 years so it costs 15 x 9 = 135

You save three years of payback (1 mark) 3 x 15 = 45 (1 mark)

(Check: 180-135 = 45)

If you got the answer to (a) wrong they let you have 2 marks for this bit if youmultiplied your answer to (a) by three.

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Yes: with the new freezer you will use less electricity and most of our electricity in theUK is produced by burning fossil fuels (1). This releases carbon dioxide into theatmosphere that contributes to global warming (1). OR less nuclear fuel is used to makeelectricity (1) so less radioactive waste (1)

No: The manufacture of the new unit will have used more energy than you will save. Youshould only buy new appliances when it is necessary to decrease the total amount of globalenergy use. (1) Also the old unit will have to be disposed of and it contains pollutants (e.g.CFCs that affect the ozone layer) (1)

You need to make a choice and then make two points!

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It will raise its temperature it will get hotter.

They also gave a mark for set up a convection current in it or decrease the density ofthe air

The rate of energy transfer would decrease. (1 mark) (It would still be transferred butat a slower rate because the speed it moves at depends on the difference in

temperature)

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It is powered by an electric pump you have to pay for electricity.

If this confused you dont worry it did me too! When it is warm outside we usuallywant it cool inside and vice versa so when/where this would be used I havent a clue!

Seems like a daft idea to me! Even though we lose energy to the outside, the airoutside our houses in winter is not warm compared to the air inside.

I checked on the web and couldnt find anything like this system! If it had included acondenser and worked like a refrigeration unit I would get it, but this??? The diagramdoesnt make sense to me if any of you can explain it to me I would be grateful!

But even if it confused you, you should still get the marks on this question Lookcarefully at the question they TELL you it is cost effective and want you to say why not how it works.All they wanted you to say was that more heat energy wastransferred into the house than was used in operating the pump (1 mark) (they told

you it was efficient so that must be the case!) so the overall energy bills were reduced(1 mark) the report said this was badly answered I wonder why! Stupid question!

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Gamma and beta

Alpha and beta (because they are charged)

Gamma

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External conditions (pressure, temperature etc) have no effect on the rate ofdecayof a sample so changing the temperature will have no effect.

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It has one more neutron in the nucleus (1 mark). They did NOT ask you whatan isotope was they did not want a general definition type of answer. Theywanted you to answer the specific question. Saying they had differentnumbers of neutrons got you no mark.

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Time to halve from 300 to 150 counts per minute is 14 days

Time to halve from 200 to 100 counts per minute is 14 days (they only expected youto do it once just do it twice to double check your maths but go with the simplehalving from the initial value)

Half life is 14 days (1 mark for answer and 1 mark for marking it on the graph how

you did it)

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A tracer has to be an atom that the system being investigated will use. Theradioactive isotope of phosphorus will be taken into the plant in exactly the samewas a non-radioactive phosphorus would be (1 mark) as it is chemically identical toit (1 mark).

The beta particles are penetrating enough to travel out through the plant andreach the geiger counter. (1 mark). They can be detected externally (1 mark).

The half life is long enough for a detailed study of growth to be carried out overthe lifetime of the plant (1 mark) any two required.

Again a biology questionusing some physics youhave to think like a

biologist thatunderstandsradioactivity. It is likethe medical use of it as atracer only we wouldnever use b-emitters likethis on humans thecancer risk would be too

great.

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Infra red has a longer wavelength than visible light but only just longer C is theanswer.

B is 10cm that would be microwaves A would be radiowaves.

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500 000 kHz is 500 000 000 Hz (1 mark) - YOU MUST KNOW YOURPREFIXES!!!

wavelength = wavespeed/frequency (1 mark)

= 300 000 000/500 000 000 = 0.6m

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The electrons in the metal vibrate at the same frequency as the radiowaves. Thiscreates an alternating voltage (1 mark) in the aerial ac voltage and/or makes analternating current flow at the same frequency (1 mark) as the radiowaves.

(They also allowed a mark for makes the aerial hotter)

This is straight from the syllabus wording! Base your revision around the syllabus it tells you what they expect you to know/recall.

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X-rays are absorbed by the atmosphere so they wouldnt reach the telescope if itwas on Earths surface.

interferred by, reflected by etc. got no mark! Some thought the telescope gaveout the X-rays! Telescopes detect e.m. radiation!

2008_Y10_Exam

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