PHY2 4th June 2015 Unofficial Markscheme Watch

Sarcastic Goats
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Well for now I'll transcribe the paper, http://imgur.com/a/sWBSn#9 has figures

1(a) Which quantities are vectors and scalars? [2]
Vector - velocity, displacement
Scalar - speed, distance

(b) A tennis ball is thrown vertically downwards and bounces on the ground, the ball leaves the hand with initial speed 1.5m/s at a height 0.65m above the ground. The ball rebounds and is caught when travelling upwards with a speed of 1.0m/s

(i) Show the speed of the ball is about 4m/s just before it strikes the ground [3]
(ii) Sketch a velocity-time graph for the verticle motion of the tennis ball[3]

(c) In a game of tennis, a ball is hit horizontally at a height of 1.2m and travels a horizontal distance of 5.0m before reaching the ground. The ball is at rest when hit. Calculate the initial horizontal velocity given to the ball when it was hit [3]

2(a) Define the moment of a force about a point [2]
The magnitude of the force multiplied by the perpendicular distance between the line of action of the force and the pivot.
(bi) Calculate the moment of force X about the pivot, state an appropriate unit [2]
12Nm
(ii) Calculate force Y [2]
444N
(iii) The extension of the spring is 15mm, calculate the spring constant, giving your answer in N/m [2]
296000
(iv) Calculate the work done on the spring to squeeze it to the position shown in figure 2 [2]
3.3J

3(a) The vehicle accelerates horizontally from rest to 27.8m/s in 4.6s. The mass of vehicle is 360kg, the mass of the rider is 82kg
(i) calculate the average acceleration during the 4.6s time interval [significant figures] [2]
6.0ms^-2
(ii) Calculate the average horizontal resultant force on the vehicle when it is accelerating [2]
2652N
(b) State and explain how the horizontal forward force on the vehicle has to change for constant acceleration to be measured from 0 to 27.8m/s [3]
(c) Add labelled force arrows to show the horizontal forces acting on the vehicle when at constant speed [2]
(d) The vehicle now operates to a constant speed of 55m/s. The useful power output of the motors is 22kW at this speed. Calculate the horizontal resistive force on the vehicle [2]
400N

4(a) Which two are properties of the material from which the wing is made? [1]
Breaking stress (?), Young Modulus
(bi) The engineer has labelled a point Q, state the name of this point [1]
Elastic limit
(ii) Use the graph to determine the Young modulus of the alluminium alloy [2]
7.1 * 10^6 Pa
(c) Show by drawing how you would expect the stress to vary with strain as the stress is reduced [2]
Straight line that meets x-axis at 0.1 (?)
(d) Calculate the volume of 25 kg of alluminium alloy (density = 2.78 x 10^3 kg/m^3) [1]
(e) 1.28% of the aluminium alloy's volume is copper, calculate the mass of pure alluminium needed to make 25kg of the alloy (pure alluminium = 2.7x10^3 kg/m^3) [2]

5(a) How does wavelength frequency and speed of light change when a ray of light travels from air into glass [2]
Speed + wavelength decrease, frequency stays the same
(bi) Determine the angle alpha [2]
In the region of 8.1
(ii) Determine the angle theta [2]
In the region of 54.5
(ci) Identify the effect that takes place at X [1]
Total internal reflection
(ii) Explain how the effect at X is used to transmit information along an optic fibre [3]

6 Discuss the formation of a stationary wave [6]
Two waves traveling on opposite directions, with same amplitude and frequency, they have nodes and anti nodes. Nodes are formed when the two waves destructively interfere, they are 180° out of phase and cause a total displacement of zero, anti nodes consecutively interfere, in phase with each other, giving the maximum displacement (positive or negative) from the equilibrium position

7(a) On the axes, sketch a graph to show how the intensity varies with position for a monochromatic light source [2]
(bi) Explain what is meant by coherent sources [1]
(ii) Explain how the single slit makes the light from the source slits coherent for fringes to be observed [1]
(iii) Explain how the fringes are formed [3]
(ci) Calculate the distance between the double slits and screen [2]
(ii) Describe the change to the pattern when the violet laser is replaced by a green laser [1]
(iii) Describe how the scientist could obtain an accurate value for wavelength [3]

Please help answer this and I'll add in the points.
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Crespo08
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(Original post by Sarcastic Goats)
Well for now I'll transcribe the paper

1(a) Which quantities are vectors and scalars?

(b) A tennis ball is thrown vertically downwards and bounces on the ground, the ball leaves the hand with initial speed 1.5m/s at a height 0.65m above the ground. The ball rebounds and is caught when travelling upwards with a speed of 1.0m/s

(i) Show the speed of the ball is about 4m/s just before it strikes the ground
(ii) Sketch a velocity-time graph for the verticle motion of the tennis ball

(c) In a game of tennis, a ball is hit horizontally at a height of 1.2m and travels a horizontal distance of 5.0m before reaching the ground. The ball is at rest when hit. Calculate the initial horizontal velocity given to the ball when it was hit

2(a) Define the moment of a force about a point
(bi) Calculate the moment of force X about the pivot, state an appropriate unit
(ii) Calculate force Y
(iii) The extension of the spring is 15mm, calculate the spring constant, giving your answer in N/m
(iv) Calculate the work done on the spring to squeeze it to the position shown in figure 2

3(a) The vehicle accelerates horizontally from rest to 27.8m/s in 4.6s. The mass of vehicle is 360kg, the mass of the rider is 82kg
(i) calculate the average acceleration during the 4.6s time interval [significant figures]
(ii) Calculate the average horizontal resultant force on the vehicle when it is accelerating
(b) State and explain how the horizontal forward force on the vehicle has to change for constant acceleration to be measured from 0 to 27.8m/s
(c) Add labelled force arrows to show the horizontal forces acting on the vehicle when at constant speed
(d) The vehicle now operates to a constant speed of 55m/s. The useful power output of the motors is 22kW at this speed. Calculate the horizontal resistive force on the vehicle

4(a) Which two are properties of the material from which the wing is made?
(bi) The engineer has labelled a point Q, state the name of this point
(ii) Use the graph to determine the Young modulus of the alluminium alloy
(c) Show by drawing how you would expect the stress to vary with strain as the stress is reduced
(d) Calculate the volume of 25 kg of alluminium alloy (density = 2.78 x 10^3 kg/m^3)
(e) 1.28% of the aluminium alloy's volume is copper, calculate the mass of pure alluminium needed to make 25kg of the alloy (pure alluminium = 2.7x10^3 kg/m^3)

5(a) How does wavelength frequency and speed of light change when a ray of light travels from air into glass
(bi) Determine the angle alpha
(ii) Determine the angle theta
(ci) Identify the effect that takes place at X
(ii) Explain how the effect at X is used to transmit information along an optic fibre

6 Discuss the formation of a stationary wave [6]

7(a) On the axes, sketch a graph to show how the intensity varies with position for a monochromatic light source [2]
(bi) Explain what is meant by coherent sources [1]
(ii) Explain how the single slit makes the light from the source slits coherent for fringes to be observed [1]
(iii) Explain how the fringes are formed [3]
(ci) Calculate the distance between the double slits and screen [2]
(ii) Describe the change to the pattern when the violet laser is replaced by a green laser [1]
(iii) Describe how the scientist could obtain an accurate value for wavelength [3]

Please help answer this and I'll add in the points.
Think velocity and displacement were the vector ones and speed and distance were scalar ones
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a.a.k
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(Original post by Crespo08)
Think velocity and displacement were the vector ones and speed and distance were scalar ones
Yes

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OscarH
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Fairly sure answer to c was 10.1

2a Definition of moment: The magnitude of the force multiplied by the perpendicular distance between the line of action of the force and the pivot.
3a 6.0ms-2 (TWO SIG FIGS)
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Sarcastic Goats
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(Original post by OscarH)
Fairly sure answer to c was 10.1

2a Definition of moment: The magnitude of the force multiplied by the perpendicular distance between the line of action of the force and the pivot.
3a 6.0ms-2 (TWO SIG FIGS)
For 1c I got 20.2 because I multiplied it by 2 due to s = (u+v)/2*t, and the question saying the ball was hit from rest

Everyone else is saying 10.1 though
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j5994
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(Original post by OscarH)
Fairly sure answer to c was 10.1

2a Definition of moment: The magnitude of the force multiplied by the perpendicular distance between the line of action of the force and the pivot.
3a 6.0ms-2 (TWO SIG FIGS)
for the definition I was stupid and wrote that ' in a system of equilibrium the sum of the clockwise moments = the sum of the anticlockwise moments' but after that I said it is the force x perpendicular distance. would I get any marks?
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Sarcastic Goats
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(Original post by j5994)
for the definition I was stupid and wrote that ' in a system of equilibrium the sum of the clockwise moments = the sum of the anticlockwise moments' but after that I said it is the force x perpendicular distance. would I get any marks?
I'd say at least 1, if you mentioned force x perpendicular that is 2 marks I think
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OscarH
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(Original post by j5994)
for the definition I was stupid and wrote that ' in a system of equilibrium the sum of the clockwise moments = the sum of the anticlockwise moments' but after that I said it is the force x perpendicular distance. would I get any marks?
That's the principle of moments. You may get a mark for saying it is force * perp distance, but you are pretty much giving two answers, depends on the examiner.
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j5994
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(Original post by OscarH)
That's the principle of moments. You may get a mark for saying it is force * perp distance, but you are pretty much giving two answers, depends on the examiner.
ugh i know im so stupid, he probably won't even read it coz he thinks its wrong
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Sarcastic Goats
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(Original post by sam/)
I got an answer of 10, I think you had to use v² = u² + 2as, as you are told that the ball is hit from rest (u = 0 m/s), the distance the ball travels (s = 5 m), and acceleration (due to gravity) is always 9.81m/s².
But isn't that the vertical velocity?
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j5994
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for question 1b proving it was bout 4ms-1 I did some kind of suvat but ended up with something like 3.57, which I rounded to 4. would I get any marks coz its not what everyone else had?
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Sarcastic Goats
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(Original post by j5994)
for question 1b proving it was bout 4ms-1 I did some kind of suvat but ended up with something like 3.57, which I rounded to 4. would I get any marks coz its not what everyone else had?
Probably not, if you're lucky you may get a method mark, but they'll definitely need 3.87 for one mark
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lolikokhh
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1(b)(ii) Would I get 1 mark for a straight line from X-Y?

3(b) Horizontal driving force makes a constant acceleration. I said that the Driving force should increase at a constant rate for a constant velocity as force is proportional to acceleration. How many marks would I get out of 3?

4(a) Is Young Modulus and Stiffness constant correct?

4(c) For this I did the line up parallel to the limit of proportionality and then a straight line to 0. Would I get 2 marks?

4(e) For this I found out the volume of the copper and then the mass. Would I get 1 mark for the volume working out?

7(a) I put the fringe spacing the same width but the intensity after the central fringe a bit less and the rest the same as that. Would I get 2 marks?

7(b)(ii) For this I said that it puts the white light into one slit of diffraction along with the double slits being an equal distance from the single slit so they are coherent. Would I get 1 mark?

7(c)(ii) Is saying the central maximum is wider correct because green light has a higher
3(b) Horizontal driving force makes a constant acceleration. I said that the Driving force should increase at a constant rate for a constant velocity as force is proportional to acceleration. How many marks would I get out of 3?4(a) Is Young Modulus and Stiffness constant correct?4(c) For this I did the line up parallel to the limit of proportionality and then a straight line to 0. Would I get 2 marks?4(e) For this I found out the volume of the copper and then the mass. Would I get 1 mark for the volume working out?7(a) I put the fringe spacing the same width but the intensity after the central fringe a bit less and the rest the same as that. Would I get 2 marks?7(b)(ii) For this I said that it puts the white light into one slit of diffraction along with the slits being an equal length from the single slit

7(c)(ii) Is saying that there is wider maxima because green light has a wider wavelength correct?

7(c)(iii) For this I said use different slit separations where it is measured with a vernier. I said take at least 8 slit separations. The single slit is not needed I said. I said measure the distance from slit to screen with a ruler with mm marking to increase accuracy and the same for fringe spacing. Then I said find wavelength with ws/D. Would I get 3 marks?

Please answer these
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xKin
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Breaking stress is different for each material, I'm sure it's one of the answers.
And graph is from X to -4, then at tA it starts at 4 at the top and goes down to Y, straight lines.
2b iv) 3.3 j
3aII) 440N
Name of the point is Yield point 4bi
4C is a line straight from 0.10 on the curve to something on the x axis greater than Q but less than 0.1
5a) wavelength decreases, freq constant, speed decreases
5ci) Total internal reflection
7bi) same frequency and constant phase relationship or difference
7cii) bigger fringe spacing so fringes are more spread out or dark fringes are wide.
Np
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the_german_boy
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(Original post by Sarcastic Goats)
Well for now I'll transcribe the paper, http://imgur.com/a/sWBSn#9 has figures

1(a) Which quantities are vectors and scalars? [2]
Vector - velocity, displacement
Scalar - speed, distance

(b) A tennis ball is thrown vertically downwards and bounces on the ground, the ball leaves the hand with initial speed 1.5m/s at a height 0.65m above the ground. The ball rebounds and is caught when travelling upwards with a speed of 1.0m/s

(i) Show the speed of the ball is about 4m/s just before it strikes the ground [3]
(ii) Sketch a velocity-time graph for the verticle motion of the tennis ball[3]

(c) In a game of tennis, a ball is hit horizontally at a height of 1.2m and travels a horizontal distance of 5.0m before reaching the ground. The ball is at rest when hit. Calculate the initial horizontal velocity given to the ball when it was hit [3]

2(a) Define the moment of a force about a point [2]
The magnitude of the force multiplied by the perpendicular distance between the line of action of the force and the pivot.
(bi) Calculate the moment of force X about the pivot, state an appropriate unit [2]
(ii) Calculate force Y [2]
(iii) The extension of the spring is 15mm, calculate the spring constant, giving your answer in N/m [2]
(iv) Calculate the work done on the spring to squeeze it to the position shown in figure 2 [2]

3(a) The vehicle accelerates horizontally from rest to 27.8m/s in 4.6s. The mass of vehicle is 360kg, the mass of the rider is 82kg
(i) calculate the average acceleration during the 4.6s time interval [significant figures] [2]
6.0ms^-2
(ii) Calculate the average horizontal resultant force on the vehicle when it is accelerating [2]
(b) State and explain how the horizontal forward force on the vehicle has to change for constant acceleration to be measured from 0 to 27.8m/s [3]
(c) Add labelled force arrows to show the horizontal forces acting on the vehicle when at constant speed [2]
(d) The vehicle now operates to a constant speed of 55m/s. The useful power output of the motors is 22kW at this speed. Calculate the horizontal resistive force on the vehicle [2]

4(a) Which two are properties of the material from which the wing is made? [1]
(bi) The engineer has labelled a point Q, state the name of this point [1]
(ii) Use the graph to determine the Young modulus of the alluminium alloy [2]
(c) Show by drawing how you would expect the stress to vary with strain as the stress is reduced [2]
(d) Calculate the volume of 25 kg of alluminium alloy (density = 2.78 x 10^3 kg/m^3) [1]
(e) 1.28% of the aluminium alloy's volume is copper, calculate the mass of pure alluminium needed to make 25kg of the alloy (pure alluminium = 2.7x10^3 kg/m^3) [2]

5(a) How does wavelength frequency and speed of light change when a ray of light travels from air into glass [2]
(bi) Determine the angle alpha [2]
(ii) Determine the angle theta [2]
(ci) Identify the effect that takes place at X [1]
(ii) Explain how the effect at X is used to transmit information along an optic fibre [3]

6 Discuss the formation of a stationary wave [6]

7(a) On the axes, sketch a graph to show how the intensity varies with position for a monochromatic light source [2]
(bi) Explain what is meant by coherent sources [1]
(ii) Explain how the single slit makes the light from the source slits coherent for fringes to be observed [1]
(iii) Explain how the fringes are formed [3]
(ci) Calculate the distance between the double slits and screen [2]
(ii) Describe the change to the pattern when the violet laser is replaced by a green laser [1]
(iii) Describe how the scientist could obtain an accurate value for wavelength [3]

Please help answer this and I'll add in the points.
2)b)i) was 12Nm
ii) was 444N I think
iii) 296000Nm^-1
iv) 3.3J - you use E=Fe, where e is extension

3)a)ii) 2652N
d) 400N

4)a) Stiffness constant and Young Modulus
b)i) Elastic limit
ii) ~7.1*10^6Pa
c) straight line that meets x axis at ~0.1

5)a) speed decreases, wavelength decreases, frequency stays the same
c)i) Total internal reflection
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-jordan-
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(Original post by xKin)
Breaking stress is different for each material, I'm sure it's one of the answers.
And graph is from X to -4, then at tA it starts at 4 at the top and goes down to Y, straight lines.
2b iv) 3.3 j
3aII) 440N
Name of the point is Yield point 4bi
4C is a line straight from 0.10 on the curve to something on the x axis greater than Q but less than 0.1
5a) wavelength decreases, freq constant, speed decreases
5ci) Total internal reflection
7bi) same frequency and constant phase relationship or difference
7cii) bigger fringe spacing so fringes are more spread out or dark fringes are wide.
Np
4bi is not the yield point. It is the elastic limit.
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xKin
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Sir, read the question, it says it's already past elastic limit. It is beyond where the behaviour of the material becomes changed irreversibly.
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mickel_w
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Can someone 100% confirm what the light intensity pattern should be.
Also, looking at the diagram alpha=8.93 and theta = 53/54, without a doubt.
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mickel_w
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(Original post by xKin)
Sir, read the question, it says it's already past elastic limit. It is beyond where the behaviour of the material becomes changed irreversibly.
Elastic limit is defined as the point beyond that the material changes irreversibly.. If it were the yield point we would see a sudden increase in strain for a constant load. This doesnt happen
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xKin
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I wouldn't say without a doubt, that question rekt, I got 8.91 and 53.5
And yes I think I read the question wrong it is Elastic limit fk me
I think they want the normal one, big peak with high intensity in the middle and gets smaller either side. It's either that or peaks have same intensity which never came on before.
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