# weight = mass x gravitational field strength

## Presentation on theme: "weight = mass x gravitational field strength"— Presentation transcript:

weight = mass x gravitational field strength
Q1 (9 marks) (a)(i) The diagram shows a cable car used to take skiers to the top of a mountain. The total mass of the cable car and skiers is 7500 kg. Use the equation calculate the weight of the cable car and skiers. weight = mass x gravitational field strength gravitational field strength = 10 N/kg Show clearly how you work out your answer and give the unit. (3)

weight = mass x gravitational field strength
Q1 (9 marks) (a) (i) The diagram shows a cable car used to take skiers to the top of a mountain. The total mass of the cable car and skiers is 7500 kg. Use the equation calculate the weight of the cable car and skiers. weight = mass x gravitational field strength gravitational field strength = 10 N/kg Show clearly how you work out your answer and give the unit. (3) weight = 7500 x 10 (1 mark) = 75,000 (1 mark) N (1 mark)

All units have to lose their prefix before being inserted into an equation EXCEPT mass which is measured in kg (which it was given in!) You must learn your units (a frightening number of you thought the unit was kilogram!) You have to get the case of the letter correct – ‘N’ was worth a mark – ‘n’ was not worth anything… if you don’t know it then write the word out in full.

work done = force applied x distance moved in the direction of force
(ii) The cable car moves at a constant speed. It lifts skiers through a vertical height of 800 metres in 7 minutes. Use the following equation to calculate the work done to lift the cable car and skiers. work done = force applied x distance moved in the direction of force Show clearly how you work out your answer. Work done = J (2 marks)

You worked out the weight in part (i)
(ii) The cable car moves at a constant speed. It lifts skiers through a vertical height (weight acts vertically – so this is the distance you need) of 800 metres in 7 minutes (time is not needed for this part of the question). You worked out the weight in part (i) Use the following equation to calculate the work done to lift the cable car and skiers. work done = force applied x distance moved in the direction of force Show clearly how you work out your answer. Work done = 75,000 x 800 (1 mark) = 60,000,000 (1 mark) Work done = 60,000,000 J (2 marks)

You could get both marks by multiplying your answer to part (i) by 800
If a question has sub-parts you usually are guided through steps in answering the question, In the old days they would have given you 5 marks for working out the work done when the cable car of mass 7500kg was raised 800m – they wouldn’t give you the equations or the clue that mass has to be converted to weight. A worrying number of you used the time info in your answers! They GIVE you the equation – time isn’t in it!

(b) The diagram shows a skier who is accelerating down a steep ski slope.
(i) Draw an arrow on the diagram to show the direction of the resultant force acting on the skier (1 mark) (ii) How and why does the kinetic energy of the skier change? (2 marks)

(b) The diagram shows a skier who is accelerating down a steep ski slope.
(i) Draw an arrow on the diagram to show the direction of the resultant force acting on the skier (1 mark) Acceleration is always in the same direction as the net force. Arrow down and parallel to the slope. (ii) How and why does the kinetic energy of the skier change? She is accelerating – getting faster – kinetic energy depends on velocity so as velocity is increasing (1 mark) the kinetic energy will increase (1 mark) (2 marks) OR As she goes down the slope gravitational potential energy is changed into kinetic energy (1 mark) – therefore the kinetic energy increases (1 mark)

A worrying number had the arrow going up the slope
A worrying number had the arrow going up the slope! The question tells you he is accelerating down! Think – if going downhill on a fixed gradient (like in the picture) you will get faster and faster – when you reach terminal velocity you will go at a steady speed – you will not slow down or slide up the slope… If the gradient of the slope got less steep the acceleration would decrease – but would still be there. To slow yourself on skis you need to dig into the snow – increase friction. Many of you did not know what kinetic energy depended on. Now that you do not have to learn equations for calculations many of you do not learn what the quantity depends on. Those who did know KE was ½ mv2 were the ones that spoke of the change in velocity. I would recommend you learnt the equations as a way of learning what the terms are.

(c) Last year, 18 000 skiers suffered a head injury
(c) Last year, skiers suffered a head injury. It is thought that nearly 8000 of these injuries could have been avoided if the skier had been wearing a helmet. However, at present, there are no laws to make skiers wear helmets. Suggest why skiers should be made aware of the benefits of wearing a helmet. (1 mark)

(c) Last year, 18 000 skiers suffered a head injury
(c) Last year, skiers suffered a head injury. It is thought that nearly 8000 of these injuries could have been avoided if the skier had been wearing a helmet. However, at present, there are no laws to make skiers wear helmets. Suggest why skiers should be made aware of the benefits of wearing a helmet. (1 mark) They should be made aware so that they are able to make an informed decision as to whether to wear one (1 mark) – OR be more likely to wear one (1 mark) OR they will know that wearing a helmet is likely to / will reduce (risk) head injury

‘Suggest why skiers should be made aware of the benefits of wearing a helmet’ was asked – a lot of you answered the question, ‘How does a helmet keep you safe?’. You went into details about how a helmet reduced pressure – good physics – but NOT what was worth a mark! Start your sentence with part of the question – then you are more likely to answer it!

Q2 (6 marks) The pie chart shows the sources of the background radiation and the radiation doses that the average person in the UK is exposed to in one year. Radiation dose is measured in millisieverts (mSv). (a) (i) What is the total radiation dose that the average person in the UK receives? Total radiation dose = mSv (1 mark)

Q2 (6 marks) The pie chart shows the sources of the background radiation and the radiation doses that the average person in the UK is exposed to in one year. Radiation dose is measured in millisieverts (mSv). (a) (i) What is the total radiation dose that the average person in the UK receives? Total radiation dose = = 2.50 mSv (1 mark)

Simple maths – but several of you couldn’t add up the numbers correctly!
In an exam add up – then add up in another order – double check your answers – the loss of 1 mark is more than 2%.. There can be as little as 2 or 3 marks between grades – meaning a 1 mark loss can mean a loss of 5 UMS score points!

(ii) A student looked at the pie chart and then wrote down three statements. Which one of the following statements is a correct conclusion from this data? In the future, more people will be exposed to a greater proportion of radon gas. People that have never had an X-ray get 50% of their radiation dose from radon gas. The radiation dose from natural sources is much greater than from artificial radon gas. (1 mark)

(ii) A student looked at the pie chart and then wrote down three statements. Which one of the following statements is a correct conclusion from this data? In the future, more people will be exposed to a greater proportion of radon gas. There is nothing about the future in the pie chart! People that have never had an X-ray get 50% of their radiation dose from radon gas. Doesn’t add up! The radiation dose from natural sources is much greater than from artificial sources. The artificial ones are nuclear and medical (1 mark)

(b) The concentration of radon gas inside a home can vary from day to day. In some homes, the level can build up to produce a significant health risk. It is estimated that each year 1000 to 2000 people die because of the effects of radiation from radon gas. (i) It is not possible to give an exact figure for the number of deaths caused by the effects of radiation from radon gas. Why? (1 mark)

(b) The concentration of radon gas inside a home can vary from day to day. In some homes, the level can build up to produce a significant health risk. It is estimated that each year 1000 to 2000 people die because of the effects of radiation from radon gas. (i) It is not possible to give an exact figure for the number of deaths caused by the effects of radiation from radon gas. Why? (1 mark) Deaths from radiation exposure are usually due to cancers – when someone gets cancer, radon may be the cause, but other factors may be involved. We are exposed to other background radiations and some chemicals are carcinogens – e.g. chemicals found in cigarettes. Therefore we cannot give an exact figure.

The table gives data for the radiation levels measured in homes in 4 different parts of the UK. The radiation levels were measured using two detectors, one in the living room and one in the bedroom. The measurements were taken over 3 months. (ii) Give one reason why the measurements were taken over 3 months using detectors in different rooms. (1 mark)

All they really wanted was that they needed to find an average.
The table gives data for the radiation levels measured in homes in 4 different parts of the UK. The radiation levels were measured using two detectors, one in the living room and one in the bedroom. The measurements were taken over 3 months. (ii) Give one reason why the measurements were taken over 3 months using detectors in different rooms. (1 mark) There will be different concentrations in different rooms (bedrooms are upstairs usually and you spend about 8 hours in the bedroom whereas the living room is downstairs and you spend about 8 hours there too – the other 8 hours is usually outside the home (school or work). Therefore putting two detectors in the house in those locations allows an average daily radon exposure due to place to be worked out. Doing this over three months allows daily fluctuations to be seen and an average over time to be calculated. All they really wanted was that they needed to find an average. That makes the result (more) reliable or valid. It does NOT make it more ‘accurate’.

(iii) Use information from the table to suggest why a much higher proportion of homes were sampled in areas C and D than in areas A and B. (2 marks)

(iii) Use information from the table to suggest why a much higher proportion of homes were sampled in areas C and D than in areas A and B. (2 marks) The average level (much) higher (in C and D) (1 mark) and maximum level (in C and D) is very high (1 mark)

Q3 (6 marks) (a) When a glass rod is rubbed with a woollen cloth, the rod becomes positively charged. (i) Explain why the glass becomes positively charged. (2 marks)

Q3 (8 marks) When a glass rod is rubbed with a woollen cloth, the rod becomes positively charged. Explain why the glass becomes positively charged. The electrons (1 mark) are transferred from the rod to the cloth (1 mark as long as the first mark was awarded) as they rub together. (2 marks)

Negative charge transfer to the cloth / removed from rod earned 1 mark
Transfer of positive charge /positive electrons scored zero Transfer of electrons to the rod scores zero An alarming number of you didn’t know that electrons were negative. That is a basic fact that you should know for Chemistry too! Those of you that spoke of ion transfer also were way off the mark! Ions in the solid stay in place – they make up the solid structure. The cloth and the rod were both neutral before the rubbing – some of you thought they were charged! The cloth is more attractive to electrons than the rod is – therefore some of the electrons move to the rod during the ‘rubbing’. The rod loses electrons therefore it is positive as it starts off neutral and loses negative charge.

ii) A glass TV screen, polished with a dry cloth on a dry day, soon becomes dusty again. Explain why
(2 marks)

ii) A glass TV screen, polished with a dry cloth on a dry day, soon becomes dusty again. Explain why
(2 marks) This is a part (ii) so it will relate to the part (i). The glass becomes (positively) charged when rubbed with the cloth. (1 mark). The dust particles are attracted (1 mark) to the screen.

A good answer will talk of induced charge on the dust particles:
When dust is near the positive screen the electrons in the dust particle move towards the part of the dust that is near the screen. This makes one side of the dust positive and one part negative. The negative side of the dust will be attracted to the positive screen and therefore it will stick to the screen and it will get very dusty.

(b) Many devices use electrostatic charge to work.
The following sentences describe how a photocopier works using electrostatic charge. The sentences are in the wrong order. J A strong light is used to form an image of the page to be copied on the roller. K The charged areas of the roller attract particles of black toner powder. L The charge left on the roller has the same pattern as the dark parts of the original page. M The toner melts and sticks to the paper. This is now a photocopy of the original. N A roller coated with a photoconducting material is given a charge. O Where light hits the roller, the charge leaks away. P A blank piece of paper is heated and pressed against the roller. (i) Arrange the sentences in the correct order (3 Marks). Three of the sentences have been put into the correct places.

(b) Many devices use electrostatic charge to work.
The following sentences describe how a photocopier works using electrostatic charge. The sentences are in the wrong order. J A strong light is used to form an image of the page to be copied on the roller. K The charged areas of the roller attract particles of black toner powder. L The charge left on the roller has the same pattern as the dark parts of the original page. M The toner melts and sticks to the paper. This is now a photocopy of the original. N A roller coated with a photoconducting material is given a charge. O Where light hits the roller, the charge leaks away. P A blank piece of paper is heated and pressed against the roller. (i) Arrange the sentences in the correct order (3 Marks). Three of the sentences have been put into the correct places.

You got three marks if the letters were all in the right places.
3 marks for 4 correct 2 marks for 2 correct 1 mark for 1 correct

(ii) Why is it important that the blank piece of paper is heated
(ii) Why is it important that the blank piece of paper is heated? (1 mark)

(ii) Why is it important that the blank piece of paper is heated
(ii) Why is it important that the blank piece of paper is heated? (1 mark) The idea is it is heated to melt the toner (to make the toner stick is acceptable unless a reason is given that infers this is due to attraction of charged particles)

Q4 (6 marks) Uranium atoms do not always have the same number of neutrons. What are atoms of the same element that have different numbers of neutrons called?

Q4 (6 marks) Uranium atoms do not always have the same number of neutrons. What are atoms of the same element that have different numbers of neutrons called? Isotopes

By emitting an alpha particle, an atom of uranium-235 decays into an atom of thorium.
An alpha particle, which is the same as a helium nucleus, is represented by the symbol The decay can be represented by the equation below. Complete the equation by writing the correct number in each of the two boxes. (2 marks)

By emitting an alpha particle, an atom of uranium-235 decays into an atom of thorium.
An alpha particle, which is the same as a helium nucleus, is represented by the symbol The decay can be represented by the equation below. Complete the equation by writing the correct number in each of the two boxes. (2 marks)

The top number is the nucleon number (a nucleon is a particle in the nucleus – a proton or neutron)
The bottom number is the proton number The top numbers should add up: 235 = unknown + 4 (so top unknown is 231) The bottom numbers should add up: 92 = unknown + 2 (so bottom unknown is 90)

The diagram shows an atom of uranium-235 being split into several pieces.
(i) Name the process shown in the diagram. (1 mark) (ii) Name the particles labelled X. (1 mark)

The diagram shows an atom of uranium-235 being split into several pieces.
(i) Name the process shown in the diagram. (1 mark) (Nuclear) fission (ii) Name the particles labelled X. (1 mark) Neutrons

(d) Uranium-235 is used as a fuel in some nuclear reactors.
Name another substance used as a fuel in some nuclear reactors. (1 mark)

(d) Uranium-235 is used as a fuel in some nuclear reactors.
Name another substance used as a fuel in some nuclear reactors. (1 mark) Plutonium (239) (the syllabus says you should know the two nuclear fuels)

Q5 (7 marks) The graphs show how the velocity of two cars, A and B, change from the moment the car drivers see an obstacle blocking the road. One of the car drivers has been drinking alcohol. The other driver is wide awake and alert. (a) (i) How does a comparison of the two graphs suggest that the driver of car B is the one who has been drinking alcohol?

Q5 (7 marks) (i) How does a comparison of the two graphs suggest that the driver of car B is the one who has been drinking alcohol? B has a longer reaction time or greater thinking distance or greater stopping distance (Can accept slower reactions or greater thinking time BUT do not accept slower reaction time).

You cannot have a slower distance! You cannot have a slower time!

(a) (ii) How do the graphs show that the two cars have the same deceleration?

(ii) How do the graphs show that the two cars have the same deceleration?
Gradients are the same – or -they both slow down from the same speed to zero in the same time interval.

(iii) Use the graphs to calculate how much further car B travels before stopping compared to car A.

(iii) Use the graphs to calculate how much further car B travels before stopping compared to car A.
Show clearly how you work out your answer. Additional stopping distance = excess area = 0.8 x 15 (2 marks) = 12 m (1 mark) – the 0.8s alone is worth 1 mark (3 marks)

You could get some of the marks by extracting CORRECT information from the graphs:
accept extracting both reaction times correctly for 1 mark (0.6s and 1.4s ) or time = 0.8s for 1 mark accept 0.8 × 15 for 2 marks accept calculating the distance travelled by car A correctly as 28.5 m or the distance travelled by car B as 40.5 m for 2 marks

This question showed that a lot of you cannot extract info from a graph… you need that skill for maths, the other sciences and geography so work on it! Several did not see that one little square represented 0.2s not 0.1s. Think! – check! – Double check! – Don’t throw away the marks! Many knew that distance was area under the graph – and then didn’t think about what was asked for and how simply it could be done…

In a crash test laboratory, scientists use sensors to measure the forces exerted in collisions. The graphs show how the electrical resistance of 3 experimental types of sensor, X, Y and Z, change with the force applied to the sensor. Which of the sensors, X, Y or Z, would be the best one to use as a force sensor? Give a reason for your answer.

Z (1 mark) – unless you got that you got no marks for this section!
Because different force values give a unique / different resistance ( 1 mark). The scientists would therefore be able to know what force was on the dummy from the electrical circuit that the sensor was put into. Do not accept force and resistance are (directly) proportional – need to say wh that is useful – unique resistance for each force. Can accept answers in terms of why either X and Y would not be the best eg X is not suitable because the same resistance value is obtained for 2 different force values and Y is not suitable because all force values give the same resistance value.

Q6 (4 marks) An oscilloscope is connected to an alternating current (a.c.) supply.The diagram shows the trace produced on the oscilloscope screen. Each horizontal division on the oscilloscope screen represents s. (a) Calculate the frequency of the alternating current supply. Show clearly how you work out your answer and give the unit. (3 marks)

Q6 (4 marks) An oscilloscope is connected to an alternating current (a.c.) supply.The diagram shows the trace produced on the oscilloscope screen. Each horizontal division on the oscilloscope screen represents s. (a) Calculate the frequency of the alternating current supply. Show clearly how you work out your answer and give the unit. (3 marks)

1 mark for numeric answer (calculation) and 1 mark for the unit
125 (2 marks) hertz or Hz (1 mark) (do not accept hz) I told you the case of the letter matters! allow 1 mark for obtaining time period = s or for stating that frequency = 1 / time period (max of 1 if they have not got the correct answer)

(b) What is the frequency of the a. c
(b) What is the frequency of the a.c. mains electricity supply in the UK?

(b) What is the frequency of the a. c
(b) What is the frequency of the a.c. mains electricity supply in the UK? 50 Hz mark is for number alone. This was pure recall – it is on the syllabus that you should know it!

Q7 (5 marks) A homeowner has installed electric underfloor heating in the kitchen. When the heating is switched on, an electric current flows through wires running under the tiled floor surface. (a) What is an electric current?

Q7 (6 marks) A homeowner has installed electric underfloor heating in the kitchen. When the heating is switched on, an electric current flows through wires running under the tiled floor surface. (a) What is an electric current? The (rate of) flow of charge (through a circuit). Accept electrons or ions instead of charge Accept movement for flow Do not accept ‘flow of electricity’

power = current x potential difference
7 (b) The graph shows how the power output of an underfloor heating system depends on the area of the floor that is heated. The area of the homeowner’s kitchen floor is 9.0 m2. Use the graph and the given equation to calculate the current drawn from the 230Vmains supply by the heating system. power = current x potential difference Show clearly how you work out your answer and give the unit.

From the graph P = 1.6 kW = 1600W P = IV so I = P/V = 1600/230 = 7.0A Unit – 1 mark - A or amp(ere) 7.0 (3 marks) accept 6.96 / 6.95 or an answer that would approximate to 6.96 if rounded allow 1 mark for obtaining correct power and changing to watts ie 1600 or allow 2 marks for correct substitution and transformation ie 1600 ÷ 230 an answer / gains 2 marks allow 1 mark for 1.6 / 230 or 1.7 / 230 an answer 7.39 or 7.4 gains 2 marks

Similar presentations