PHY2 4th June 2015 Unofficial Markscheme

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

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)

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?

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.

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.

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?

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.

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

Sir, read the question, it says it's already past elastic limit. It is beyond where the behaviour of the material becomes changed irreversibly.