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# Ocr gateway p1 p2 p3 15/06: Officialthread Watch

1. (Original post by xxxxhunterxxxx)
i got 28000 for the last one. There were two formulas for power.Shouldnt both formulas yield the same answer. I'm so confused!!!!!!
It was 2800N * 20 m/s = 56000 W?
2. (Original post by Chittesh14)
Sorry, the answers at 40 and 60. I just realised I multiplied by mass by the specific heat capacity twice. ****.
Lol oh well

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3. What was the answer to that stupid acceleration and speed graph one?

What happens to the acceleration as the speed increases? The graph seriously was confusing, the acceleration decreased so I wrote it decreased as the speed increases.
But, in reality like science, the speed increases so the acceleration increases?
4. (Original post by Chittesh14)
It was 2800N * 20 m/s = 56000 W?
there was another formula:
power=workdone/time
so i did 280000/10
5. Regarding the P3 [6] marker, were these correct?

Part A = speed increases, acceleration
Part B = speed constant, no acceleration
Part C = speed decreases, deceleration
Part D = no speed, car is at rest.
6. (Original post by xxxxhunterxxxx)
there was another formula:
power=workdone/time
so i did 280000/10
Ah, but it specifically said use the information from part b as in the force (2800 N).
I have no idea tbh bro, I am sure it was 56, 000.
There must've been a way, but I am unsure.
7. (Original post by Chittesh14)
Regarding the P3 [6] marker, were these correct?

Part A = speed increases, acceleration
Part B = speed constant, no acceleration
Part C = speed decreases, deceleration
Part D = no speed, car is at rest.
yeah, but i also said that half way through A he hit a constant speed .Cos the curve straightens up. kinda hard to explain.
8. (Original post by Chittesh14)
Ah, but it specifically said use the information from part b as in the force (2800 N).
I have no idea tbh bro, I am sure it was 56, 000.
There must've been a way, but I am unsure.
oh right- i didnt read that bit. thanks though.
9. (Original post by xxxxhunterxxxx)
oh right- i didnt read that bit. thanks though.
No problem buddy, I didn't read many questions properly either. Very very silly mistakes, I should've cross-checked my answers lol but I didn't FFS!
10. (Original post by Chittesh14)
What was the answer to that stupid acceleration and speed graph one?

What happens to the acceleration as the speed increases? The graph seriously was confusing, the acceleration decreased so I wrote it decreased as the speed increases.
But, in reality like science, the speed increases so the acceleration increases?
Yeah that trend is right because you see with the parachute example, when speed increases, the air resistance increases also so it cause you to begin to decelerate and reach a terminal speed.

Also, for the p3 six marker, I worked out the speeds and the average accelerations as well- is that ok???? I said accelerating, constant speed, negative acceleration and stationary as well?
11. (Original post by leopard923)
Yeah that trend is right because you see with the parachute example, when speed increases, the air resistance increases also so it cause you to begin to decelerate and reach a terminal speed.

Also, for the p3 six marker, I worked out the speeds and the average accelerations as well- is that ok???? I said accelerating, constant speed, negative acceleration and stationary as well?
Oh my God, you are a genius.
But, did it talk about a parachutist in the question? - tricky one.
I didn't talk about the air resistance, I said something so idiotic.
12. (Original post by leopard923)
Yeah that trend is right because you see with the parachute example, when speed increases, the air resistance increases also so it cause you to begin to decelerate and reach a terminal speed.

Also, for the p3 six marker, I worked out the speeds and the average accelerations as well- is that ok???? I said accelerating, constant speed, negative acceleration and stationary as well?
Yeah, it's absolutely fine. The car is at rest/stationary is correct.
You could talk about acceleration and add data, it wasn't really needed I guess (the data).
I only talked about the data in like 1 of them where the speed was constant, so the speed was 20 m/s because the distance was 200m and time 10s - you could actually calculate it.
Other data you could talk about is just the speed was double in Part B because the car travelled twice as much etc or Part C is exactly the same as Part A so they have same average speed.
13. (Original post by Chittesh14)
Oh my God, you are a genius.
But, did it talk about a parachutist in the question? - tricky one.
I didn't talk about the air resistance, I said something so idiotic.
LOOL no I don't think I am. And no it didn't but I adapted it to the question talking about drag instead . So yeah the forces balance like with the parachute- same principle I made some stupid mistakes as well lool
14. Should I make an unofficial mark scheme?
15. (Original post by some-student)
Should I make an unofficial mark scheme?

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16. (Original post by Chittesh14)
Yeah, it's absolutely fine. The car is at rest/stationary is correct.
You could talk about acceleration and add data, it wasn't really needed I guess (the data).
I only talked about the data in like 1 of them where the speed was constant, so the speed was 20 m/s because the distance was 200m and time 10s - you could actually calculate it.
Other data you could talk about is just the speed was double in Part B because the car travelled twice as much etc or Part C is exactly the same as Part A so they have same average speed.
Ok phew because I know the other calculations are generally just estimates but I thought I should do them in case .

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17. (Original post by leopard923)

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It'll take a while but I'll post it as I go
18. (Original post by leopard923)
Ok phew because I know the other calculations are generally just estimates but I thought I should do them in case .

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Ah right :P. Well done, I'm happy you did because that was need for Level 3 haha.
I could've got 60+/75, but it seems like after reading 5 questions incorrectly, 52/75. I'm literally going nuts.
19. OCR PHYSICS B: GATEWAY SCIENCE
P1, P2, P3 EXAM (75 marks) - 15 JUNE 2016
UNOFFICIAL MARK SCHEME
This may not all be right, but I'll try and use the specification where possible, so feel free to correct me

Module P1 - 25 marks
1. Hole in the ozone layer
a) Describe what the industry were told to do after the discovery of the ozone layer hole [1]
stop using / producing CFCs (1)

b) Describe what the public were told to do after the discovery of the ozone layer hole [1]
stop using CFCs / adequate sun protection e.g. sun block (1)

c) Some scientists were skeptical. Describe how the scientists verified their information [1]
using existing scientific ideas (1)

d) Suggest why scientists are more confident now [1]
one of
• measurements repeated with new equipment (1)
• measurements repeated by different scientists (1)
• predictions tested based on the explanation (1)

2. Efficiency and Sankey diagrams
a) Calculate the energy wasted [1]
1800J (1) I think

b) Calculate the efficiency [2]
60% (2)
incorrect answer with workings (1)

c) Explain why the slow cooker takes the longest to cook but is most efficient [3]
takes the longest as it transfers the least amount of useful energy per second (using data) (1)
calculation of efficiency for slow cooker (1)
compared with calculation for efficiency of microwave, and grill (1)

3. Home insulation
a) Using a table, explain why Ivy may not want double glazing [2]
calculation of payback time: 25 years (1)
it would take a long time for her to get money back (1)

b) Given a thermogram of her house - explain it [2]
red and yellow: high heat loss (hot) (1)
black: low heat loss (cold) (1)

c) Given a diagram of double glazing - explain how hot air transfers energy to cold air outside [6]
marking points:
trapped air between glass is poor conductor - arrangement of particles being looser - and so heat will take longer to conduct out through panes of glass

trapped air also reduces convection currents and so heat cannot be transferred out by conduction, reducing heat loss

may conduct out through bricks and plastic

4. Water experiment
a) Explain how convection currents work in the water [2]
expansion when fluid is heated causes a change of density (1)
results in (bulk) fluid flow, in a convection current (1)

b) Calculate temperature rise in water and beaker [2]
energy = mass x SHC x temperature change
temperature change = energy / (mass x SHC)

may have got them the wrong way round (can't remember):
water: 60 (1)
beaker: 40 (1)

c) When heated, water heats up, then heats plastic beaker. Explain why the plastic heats up less in the microwave oven [1]
microwaves only heat water particles, not plastic particles (1)

Module P2 - 25 marks
5. Photocells
a) Apart from being used in remote locations, state two advantages of photocells [1]
any two of
• low maintenance
• no need for power cables
• no need for fuel
• long life
• renewable energy resource
• no polluting waste

b) Explain how they generate electricity [2]
• electrons are knocked loose from the siliconatoms in the crystal by the sunlight (1)
• electrons flow freely - which is a current (1)

c) These photocells do not face the sun at all times and cannot turn. Explain why they have a large surface area [2]
larger surface area means more electricity generated (1)
can be stored (in the battery) for times when it is not facing the sun (1)

6. Global warming / greenhouse effect
a) Describe the main sources of the greenhouse gases [3]
water vapour: bodies of water, e.g. oceans/lakes/seas/rivers (1)

carbon dioxide: burning of fossil fuels/respiration/deforestation (1)

methane: cattle farming/volcanoes (1)

b) What happens to some infrared from the Sun? [1]
it is absorbed by the atmosphere (1)

c) Anita: "I disagree with global warming becase the summers and winters are getting colder" - describe her observations and conclusions and explain why she may be wrong [2]
she believes that global warming cannot be happening because summers and winters are getting colder, not warmer (1)

she may be wrong asvolcanic ash and gases reflect radiation from the Sun back into space causing cooling (1)

d) Describe one natural phenomenon that causes global warming [1]
respiration (1) ? not sure

7. Energy / power
a) Pick which appliance has the highest current and calculate its current (2 decimal places) [3]
oven (1)

then

current = 7.82608696 = 7.83A (2)
correct calculation but not to 2 decimal places (1)
incorrect calculation with working (1)

b) 18p per kWh - calculate the cost of running an appliance for 20 hours (in table: 1500W in 0.5 hours) [2]
1500W = 1.5kW
for 1 hour: 3kWh
for 20 hours: 60kWh

cost = 60 x 18 = 1080 pence (2)
incorrect calculation with working (1)

c) Power company transmits electricity at 40000V to reduce energy waste - explain how [2]
an increased voltage reduces current (1)

decreasing energy waste by reducing heating of cables (1)

8. Decide which type of radiation is emitted by each source [6]
I may have remembered the radiations emitted wrong, but the first two only emitted one, and the last two emitted two

Marking points
Source A: Gamma - use of count rate from tableSource B: Alpha - use of count rate from table
Source C: Alpha & Gamma - use of count rate from table
Source D: Alpha & Beta - use of count rate from table
Fluctuations in readings are likely due to poor quality of equipment

Module P3 - 25 marks
9. Speed
a) For each diagram, tick the appropriate box [2]
the numbers and order may be wrong, but it was like this
(<= 1000N 800N => ) deceleration
(<= 800N 800N => )steady speed
(<= 800N 1000N => )accelaration

3 right (2)
2 right (1)
otherwise (0)

b) Speed acceleration graph - negative gradient curve
b)i) Describe how the acceleration changes with speed [1]
as speed increases, acceleration decreases (1)

b)ii) Explain the shape of the graph [2]
this may not be right
as the speed increases, the resistance forces increase, causing a drop in acceleration (1)
balanced forces / terminal velocity (1)

10. Car safety
a) Explain how scientists improve and compare the design of seatbelts [2]
use of test data (1)
sharing results (1)

b) Explain how seatbelts reduce the likelihood of injury [2]
spread change in momentum over a longer period of time (1)
reducing force (equation may be used) (1)

c) Apart from seatbelts, list two similar car safety features [1]
any two of
heating in brakes
crumple zones
airbags

11. Braking distance
a) Given data - "as speed doubles, so does braking distance": explain if they are right or wrong [2]
(they are wrong) no marks just for this - award no marks if they say they are correct

as speed doubles, braking distance quadruples (1)
use of KE = 1/2mv2 to explain (1)

b) Apart from high speeds, list two factors that increase braking distance [1]
• car conditions

12. Explain the distance-time graph for the bus in terms of speed and acceleration - you may include a calculation [6]
Marking points
acceleration at section A
constant speed (no acceleration) at section B - calculation of speed from graph
deceleration at section C
no speed or acceleration at section D

13. Calculations
a) Pick the acceleration from the list [1]
2m/s2 (1)

b) Calculate the work done (force: 2800N) [3]
work done = force x distance

s = t(u + v) / 2 = 10(0 + 20) / 2 = 100m

work done = 2800 x 100 = 280000J

280000J (3)
incorrect answer with working (1 or 2) I don't know what marks would be awarded

c) Calculate the power (force: 2800N) [2]
I can't remember it completely but I think it is like this
power = force x speed

5600W (2)
incorrect answer with working (1)
20. (Original post by Chittesh14)
Ah right :P. Well done, I'm happy you did because that was need for Level 3 haha.
I could've got 60+/75, but it seems like after reading 5 questions incorrectly, 52/75. I'm literally going nuts.
Really? Oh well that's makes me happier lool and I hope you do well! 52 was an a* so you could still get it!!!!

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