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# Physics edexcel igcse Watch

1. 1.a)
Constant velocity with horizontal line. (1)

1.b)
Distance travelled is area under line. (1)

1.c)
Average velocity is distance moved / time taken. (1)

2.a)
Coolant to reduce energy.Shielding to absorb radiation.Fuel rods for Uranium fuel. (2)

2.b)
Kinetic energy. (1)

2.c)
The purpose of the moderator is to slow down fast moving neutrons to become slow moving thermal neutrons. This makes it easier for neighbouring uranium nuclei to absorb the neutrons and hence go under fission. (2)

2.d)
A controlled chain reaction where only 1 out of 3 (on average) of the neutrons emitted through fission are absorbed by neighbouring uranium nuclei. This is helped by using boron control rods to absorb these remaining neutrons. This prevents an uncontrolled chain reaction. The neutron which is absorbed by a uranium nucleus becomes unstable hence splits into 2 daughter nuclei and 2-3 fast moving neutrons. This process keeps repeating. (3)

3.a)
Pressure is P1V1 = P2V2 so: (101*1700)/12 = 14308.3kPa. (3)

3.b)
Pressure with depth = height x density x g. (1)

3.c)
113.08kPa. (3)

3.d)
113.08 + 101 = 214.08kPa. (1)

3.e)
Bubbles get larger as they rise due to the decrease in pressure with the decrease in depth as pressure = hpg, so air expands into larger volume. Also, smaller bubbles join together to form larger bubbles. (2)

4.a)
Gamma for tracing.X-rays for internal objects.Microwaves for food. (3)

4.b)
Particles carrying the energy (vibrations) travel perpendicular to the direction of the wave in motion. (1)

4.c)
You have to half the time because the time measured was for the wave travelling to the point of reflection and back as the sound wave travelled double the distance (to what you are measuring) so to get the depth from the point of emission to reflection, the time is divided by 2. (2)

4.d)
As v = frequency x wavelength, upon entering a denser medium the speed of sound increases as the wavelength increases. (2)

5.a)
Draw voltmeter parallel to LDR. (1)

6.a)
DC current is current that flows in one direction. (1)

6.b)
You can measure resistance by taking voltmeter reading (ensure it is constant) and ammeter reading and then do R = V/I (Ohms). (2)

6.c)
Graph. (4)

6.b)
The purpose for the split ring commutator and carbon brushes is so that once the coil goes past the half turn, when the coil retouches the commutator the direction of the current reverses hence magnetic field hence the effect of the force on the coil, ensuring it travels unidirectionally. (1)

6.c)
The coil continues to rotate clockwise. (1)

7.a)
Refractive index in glass is higher than air. YES
If i = 0, the ray doesn't deviate. YES
All rays that enter are totally internally reflected. NO (4)

7.b)
Draw point on graph. (1)

7.c)
It fits with correlation and gradient of graph as point is plotted above point following. (1)

7.d)
Refractive index can't be 0, only <1. (1)
Critical angle can't be 0. (1)

7.e)
Critical angle was 41.82 so rounds to 42. (3)

7.f)
Refractive index is the simplest ratio between speed of light in air: speed of light in material medium. (2)

8.a)
Ruler. (1)

8.b)
Hooke's law: Measure length of spring using ruler. Add 1N mass, measure new length, subtract original length from this to get extension. Repeat this process for a range of masses. Repeat whole experiment x3 and average for increased reliability. Plot graph of extension vs load, if follows Hooke's law, the gradient line between points will be contrast as F = ke (extension is proportional to the load). (5)

9.a)
5.3 cm. (2)

9.b)
5.12cm (1)

10.a)
P = IV (1)

10.b)
Max power = (4000*600)/1000000 = 2.4 MJ. (2)

10.c)
Work done = Force x distance

10.d)
76000000J of energy. (3)

10.d)
35.02 seconds. (2)

10.e)
Decreasing power increases time taken for the same amount of work done. (1)

11.a)
KE = 1/2 x m x v(squared). (1)

11.b)
Velocity = 12m/s. (3)

11.c)
GPE = mxgxh. (1)

11.d)
GPE is gained as the lift moves up from platform to surface hence increase in height hence increase in GPE. (2)

11.e)
Slope up causes transfer of KE to GPE hence decrease in velocity hence deceleration hence less work required by brakes. Slope down converts GPE into KE hence increase in speed hence acceleration hence less work required by motor. Energy is conserved. (4)

12.a)
Sky has lowest temperature and snow and bear have same temperature which is warmer. (2)

12.b)
Hair acts as an insulator by trapping in a pocket of air, hence preventing heat loss via convection as convection requires for the movement of gas particles. (2)

12.c)
Snow was best at reflecting, worst at absorbing. Sky and polar bear good at absorbing, bad at reflecting. (2)

12.d)
UV is not reflected by the sky, it is absorbed. (1)

12.e)
Hence with white fur on top, it increases the surface area of the fur exposed to the air, minimising loss of thermal energy via radiation. By having the black skin underneath, it limits heat loss via radiation and any heat that is radiated is reflected back by fur hence retaining heat. (4)

12.f)
UV waves don't reach skin as they are good absorbers, bad reflectors hence do not undergo total internal reflection hence doesn't reach skin. (3)
2. Its Kinetic energy because When neutrons collide with uranium nucleus , A three Fast moving Neutrons are Split along with two daughter nucleus . SO in case Fast moving is the kinetic energy so It produces kinetic energy mainly
3. (Original post by shahida sulaiman)
how do u know ???? pleeeeeeeese explain!!!!
Syllabus statement 7.17:understand that a nucleus of U-235 can be split (the process of fission) by collision with a neutron, and that this process releases energy in the form of kinetic energy of the fission products.Hell yeah I do my research
4. (Original post by shahida sulaiman)
i don't get it isn't it converted in to heat ??? and to think with logic how can a reactor produce kinetic its not moving or any thing right!!!!!????
kinetic energy is when there is a lot of energy which forms movement and in nuclear fission lots of kinetic energy is produced which causes the neutrons to collide with the other nuclei which causes a chain reaction
5. (Original post by asd.987)
Syllabus statement 7.17:understand that a nucleus of U-235 can be split (the process of fission) by collision with a neutron, and that this process releases energy in the form of kinetic energy of the fission products.Hell yeah I do my research
ok thanx!!!
6. (Original post by Vigster)
1.a)
Constant velocity with horizontal line. (1)

1.b)
Distance travelled is area under line. (1)

1.c)
Average velocity is distance moved / time taken. (1)

2.a)
Coolant to reduce energy.Shielding to absorb radiation.Fuel rods for Uranium fuel. (2)

2.b)
Kinetic energy. (1)

2.c)
The purpose of the moderator is to slow down fast moving neutrons to become slow moving thermal neutrons. This makes it easier for neighbouring uranium nuclei to absorb the neutrons and hence go under fission. (2)

2.d)
A controlled chain reaction where only 1 out of 3 (on average) of the neutrons emitted through fission are absorbed by neighbouring uranium nuclei. This is helped by using boron control rods to absorb these remaining neutrons. This prevents an uncontrolled chain reaction. The neutron which is absorbed by a uranium nucleus becomes unstable hence splits into 2 daughter nuclei and 2-3 fast moving neutrons. This process keeps repeating. (3)

3.a)
Pressure is P1V1 = P2V2 so: (101*1700)/12 = 14308.3kPa. (3)

3.b)
Pressure with depth = height x density x g. (1)

3.c)
113.08kPa. (3)

3.d)
113.08 + 101 = 214.08kPa. (1)

3.e)
Bubbles get larger as they rise due to the decrease in pressure with the decrease in depth as pressure = hpg, so air expands into larger volume. Also, smaller bubbles join together to form larger bubbles. (2)

4.a)
Gamma for tracing.X-rays for internal objects.Microwaves for food. (3)

4.b)
Particles carrying the energy (vibrations) travel perpendicular to the direction of the wave in motion. (1)

4.c)
You have to half the time because the time measured was for the wave travelling to the point of reflection and back as the sound wave travelled double the distance (to what you are measuring) so to get the depth from the point of emission to reflection, the time is divided by 2. (2)

4.d)
As v = frequency x wavelength, upon entering a denser medium the speed of sound increases as the wavelength increases. (2)

5.a)
Draw voltmeter parallel to LDR. (1)

6.a)
DC current is current that flows in one direction. (1)

6.b)
You can measure resistance by taking voltmeter reading (ensure it is constant) and ammeter reading and then do R = V/I (Ohms). (2)

6.c)
Graph. (4)

6.b)
The purpose for the split ring commutator and carbon brushes is so that once the coil goes past the half turn, when the coil retouches the commutator the direction of the current reverses hence magnetic field hence the effect of the force on the coil, ensuring it travels unidirectionally. (1)

6.c)
The coil continues to rotate clockwise. (1)

7.a)
Refractive index in glass is higher than air. YES
If i = 0, the ray doesn't deviate. YES
All rays that enter are totally internally reflected. NO (4)

7.b)
Draw point on graph. (1)

7.c)
It fits with correlation and gradient of graph as point is plotted above point following. (1)

7.d)
Refractive index can't be 0, only <1. (1)
Critical angle can't be 0. (1)

7.e)
Critical angle was 41.82 so rounds to 42. (3)

7.f)
Refractive index is the simplest ratio between speed of light in air: speed of light in material medium. (2)

8.a)
Ruler. (1)

8.b)
Hooke's law: Measure length of spring using ruler. Add 1N mass, measure new length, subtract original length from this to get extension. Repeat this process for a range of masses. Repeat whole experiment x3 and average for increased reliability. Plot graph of extension vs load, if follows Hooke's law, the gradient line between points will be contrast as F = ke (extension is proportional to the load). (5)

9.a)
5.3 cm. (2)

9.b)
5.12cm (1)

10.a)
P = IV (1)

10.b)
Max power = (4000*600)/1000000 = 2.4 MJ. (2)

10.c)
Work done = Force x distance

10.d)
76000000J of energy. (3)

10.d)
35.02 seconds. (2)

10.e)
Decreasing power increases time taken for the same amount of work done. (1)

11.a)
KE = 1/2 x m x v(squared). (1)

11.b)
Velocity = 12m/s. (3)

11.c)
GPE = mxgxh. (1)

11.d)
GPE is gained as the lift moves up from platform to surface hence increase in height hence increase in GPE. (2)

11.e)
Slope up causes transfer of KE to GPE hence decrease in velocity hence deceleration hence less work required by brakes. Slope down converts GPE into KE hence increase in speed hence acceleration hence less work required by motor. Energy is conserved. (4)

12.a)
Sky has lowest temperature and snow and bear have same temperature which is warmer. (2)

12.b)
Hair acts as an insulator by trapping in a pocket of air, hence preventing heat loss via convection as convection requires for the movement of gas particles. (2)

12.c)
Snow was best at reflecting, worst at absorbing. Sky and polar bear good at absorbing, bad at reflecting. (2)

12.d)
UV is not reflected by the sky, it is absorbed. (1)

12.e)
Hence with white fur on top, it increases the surface area of the fur exposed to the air, minimising loss of thermal energy via radiation. By having the black skin underneath, it limits heat loss via radiation and any heat that is radiated is reflected back by fur hence retaining heat. (4)

12.f)
UV waves don't reach skin as they are good absorbers, bad reflectors hence do not undergo total internal reflection hence doesn't reach skin. (3)
how do u know all these answers and they r all correct 100%
7. These answers are making me feel better and slightly worse at the same time because I kind of wrote most of these things. At least I know I probably got the maths right.
8. It can be Calculated by the equation Pressure Into Volume= Pressure2 into Volume 2
9. anyone else still thinking bout this exam?

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