Q1. (a) Complete the table to show the four fundamental forces and their corresponding exchange particles.

(2)

fundamental force corresponding exchange particle

strong nuclear gluon

electromagnetic

W+W Z0

gravitational graviton

(b) Name the physical quantity that a particle must have for the electromagnetic force to act on it.

........................................................................................................................

(1)

(c) Name the particle believed to be responsible for mass. ........................................................................................................................

(1) (Total 4 marks)

Page 1 of 33

Q2. The figure below shows part of the path of a proton in a cyclotron. The proton is moving in a circular path of radius 0.20 m when it reaches the gap between the two dees at P. The gap is 25 mm wide. At P, the proton is travelling at 726 km s1 and its kinetic energy is 2750e V. On reaching the gap the proton is accelerated by a uniform electric field, produced by a potential difference of 370 V between the dees.

(a) (i) Calculate the acceleration of the proton that is produced by the electric field in the gap.

acceleration .........................................................m s2

(3)

Page 2 of 33

(ii) Show that the energy of the proton after crossing the gap is about 5 1016 J and go on to calculate the speed of the proton after being accelerated across the gap.

proton speed ..........................................................m s1

(4)

(iii) Calculate the time taken for the proton to cross the gap.

time to cross the gap ..........................................................s (2)

(b) Protons travelling at a speed v within a dee are moving in a magnetic field and follow a semicircular path of radius r.

(i) Show that r = kv, where k is a constant.

(3)

Page 3 of 33

(ii) Calculate the magnetic flux density in the dees. Give an appropriate unit for your answer.

flux density ..................................................... unit .......................... (3)

(c) In a cyclotron, the magnetic flux density and the frequency of the accelerating potential difference remain constant as the particle energy increases. In the synchrotron, they both have to change. Explain these differences in the operation of the accelerators.

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(4)

(d) Although originally used as research tools in universities, some hospitals now have their own cyclotrons. State what use a hospital might make of its cyclotron and give one advantage of the hospital having its own cyclotron on site rather than making use of a cyclotron that is some distance away.

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(2) (Total 21 marks)

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Q3. The figure below shows part of the discharge curve for a capacitor that a manufacturer tested for use in a heart pacemaker.

The capacitor was initially charged to a potential difference (pd) of 1.4 V and then discharged through a 150 resistor.

(a) Show that the capacitance of the capacitor used is about 80 F. ........................................................................................................................

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(3)

(b) Explain why the rate of change of the potential difference decreases as the capacitor discharges.

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(3)

Page 5 of 33

(c) Calculate the percentage of the initial energy stored by the capacitor that is lost by the capacitor in the first 0.015 s of the discharge.

energy lost .........................................................% (3)

(d) The charge leaving the capacitor in 0.015 s is the charge used by the pacemaker to provide a single pulse to stimulate the heart.

(i) Calculate the charge delivered to the heart in a single pulse.

charge .........................................................C (1)

(ii) The manufacturer of the pacemaker wants it to operate for a minimum of 5 years working at a constant pulse rate of 60 per minute. Calculate the minimum charge capacity of the power supply that the manufacturer should specify so that it will operate for this time. Give your answer in amp-hours (Ah).

minimum capacity .........................................................Ah (2)

(Total 12 marks)

Q4. (a) Complete the following equation to describe the decay of potassium40 emission.

(2)

Page 6 of 33

(b) When a sample of potassium-40 decays, the emitted particles have a range of energies from almost zero to a maximum value, E

max. The spectrum of energies observed is shown

in the figure below.

energy, E, of emitted particle / arbitrary units

Explain how this evidence led Pauli to predict the existence of a previously unidentified particle.

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(3) (Total 5 marks)

Q5. The bombardment of protons by other particles at Stanford University in 1968 provided evidence for the existence of quarks. Name the particles used and describe how the experiment provided the evidence.

particles.................................................................................................................

evidence................................................................................................................

.................................................................................................................................

.................................................................................................................................

.................................................................................................................................

(Total 3 marks)

Page 7 of 33

Q6. The diagram below shows one arrangement for measuring the strength of the magnetic field produced by a pair of magnets in a laboratory.

The wire is perpendicular to the magnetic field of the magnet and carries a current of 5.0 A in the direction shown. The length l of the wire shown in the diagram is 6.5 cm. The wire is held rigidly in place so that it cannot move. When the current is turned on, the reading on the balance increases.

(a) (i) Show, on the figure above, the direction of the magnetic field between the magnets that produces the increase in the balance reading.

(1)

(ii) The minimum change in reading that the balance can detect is 1 mg. Calculate the smallest change in magnetic flux density that is detectable using this arrangement. Give an appropriate unit for your answer.

change in flux density .......................... unit ................. (3)

(b) Magnetic flux density is a vector quantity. State and explain how the balance reading would be affected by rotating the pair of magnets about the vertical axis shown in the figure above.

........................................................................................................................

........................................................................................................................

(2)

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(c) Archaeologists need to detect small changes in magnetic flux density when investigating sites. This is possible using the precession of protons in a proton magnetometer.

Explain what is meant by precession. You may use a diagram to help your explanation. Go on to explain how a proton magnetometer works. Make clear in your answer what quantity is measured by a proton magnetometer to indicate changes in the magnetic flux density in the region being investigated.

The quality of your written communication will be assessed in your answer. (6)

(Total 12 marks)

Q7. Figure 1 shows the path of electrons that have been accelerated in an electron gun and then pass through a velocity selector.

Figure 1

(a) (i) Electrons are produced at the cathode of the electron gun by thermionic emission. Explain what is meant by thermionic emission and why electrons produced are likely to have a range of speeds.

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(2)

Page 9 of 33

(ii) The diagram shows the path of electrons that are moving at a speed of 4.5 107 ms1. Calculate the accelerating potential difference between the cathode and anode in the electron gun that is required to produce electrons travelling at this speed. Assume that the electrons have zero velocity when they leave the cathode. Neglect the relativistic change in mass.

accelerating pd ................................................ V (3)

(b) In the shaded region shown in Figure 1 it is possible to have either an electric field or a magnetic field, or both types of field at the same time when operating as a velocity selector. In the situation shown in Figure 1 there is a magnetic field but no electric field.

(i) Place a tick in the box that corresponds to the correct direction of the magnetic field.

Explain how you decided on your answer.

...............................................................................................................

...............................................................................................................

(2)

Towards A

Towards B

Into the page

Out of the page

Page 10 of 33

(ii) The magnetic flux density of the magnetic field is 1.4 mT. Calculate the radius of the path of electrons that move at 4.5 107ms1. Neglect the relativistic change in mass.

radius ................................................ m (3)

(c) (i) Show that the theory of relativity predicts that the percentage change in the mass of an electron as it accelerates from rest to 4.5 107 ms1 is about 1%.

percentage change in mass ................................. % (4)

(ii) State and explain the effects that the relativistic increase in mass would have on your answers for the accelerating potential difference calculated in part (a)(ii) and the radius of the path calculated in part (b)(ii). potential difference ...............................................................................

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...............................................................................................................

path radius ............................................................................................

...............................................................................................................

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(2)

Page 11 of 33

(d) A potential difference is now applied across the gap between the plates A and B. This produces a uniform electric field in the shaded region between the metal plates in addition to the magnetic field of 1.4 mT. Electrons travelling at 4.5 107 ms1 now pass straight through the velocity selector, as shown in Figure 2.

Figure 2

(i) State and explain which one of the metal plates A or B is positive. ...............................................................................................................

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...............................................................................................................

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(2)

(ii) The metal plates are 35 mm apart. Calculate the potential difference between the plates so that there is no deflection of the electron beam.

potential difference ................................................ V (4)

(Total 22 marks)

Page 12 of 33

Q8. Rutherford bombarded nitrogen with alpha particles using the experimental arrangement shown in the figure below.

The presence of a previously unknown particle X was detected using the fluorescent screen.

(i) Explain how Rutherford knew that a new particle was being detected using the fluorescent screen.

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........................................................................................................................

........................................................................................................................

........................................................................................................................

(2)

(ii) The nuclear equation below describes the bombardment of nitrogen with alpha particles. Complete the nuclear equation by adding the proton and nucleon numbers

(2)

(iii) Identify particle X. ........................................................................................................................

(1) (Total 5 marks)

Page 13 of 33

Q9. (a) A cyclotron is used to accelerate protons. The cyclotron frequency, f, is 23 MHz. (i) Explain how a proton is accelerated in the cyclotron.

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(3)

(ii) Show that the cyclotron frequency is given by:

where m is the mass of a proton, B is the magnetic flux density in the Dees and Q is the proton charge.

(2)

(iii) Calculate the magnetic flux density in the Dees of the cyclotron.

magnetic flux density ........................................... T (2)

Page 14 of 33

(b) The figure below shows the arrangement of drift tubes in a linear accelerator (LINAC).

(i) Explain why the length of the drift tubes increases along the direction of travel of the protons.

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(2)

(ii) Explain why the increase in length between successive drift tubes gets smaller towards the high-energy end of the LINAC.

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(3)

Page 15 of 33

(iii) Physicists often use LINACs to produce proton-proton collisions. State what the physicists expect to observe as a result of such collisions and why it is advantageous to use two beams of moving protons instead of one beam aimed at a stationary target.

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(3) (Total 15 marks)

Q10. The figure below shows the view from above of a roundabout in a childrens playground.

The roundabout has a moment of inertia of 240 kg m2 and is initially stationary. A child exerts a force, F, of constant magnitude on the roundabout. The force is applied 1.3 m from the axis of rotation and at an angle of 70 to one of the metal bars, as shown in the figure above. The force produces a torque of 30 N m.

(a) Calculate the magnitude of the force F.

force F ........................................... N (2)

Page 16 of 33

(b) The child pushes with force F for half a revolution of the roundabout. The child stops running and then jumps on to the moving roundabout. (i) Show that the angular speed of the roundabout before the child jumps on is about 0.9

rad s1. Assume that frictional forces in the roundabout are negligible.

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(5)

(ii) When the child gets on to the roundabout the moment of inertia increases by 45 kg m2.

Calculate the time taken for one revolution of the roundabout immediately after the child jumps on. Assume that air resistance and frictional forces at the axle of the roundabout are negligible.

time taken ............................................ s (4)

Page 17 of 33

(iii) Calculate the decrease in the rotational kinetic energy when the child jumps onto the roundabout.

decrease in kinetic energy ............................................ J (3)

(iv) Explain why the kinetic energy decreases. ...............................................................................................................

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(1)

(c) (i) Explain why the child is accelerating when on the roundabout even though the speed of rotation is constant.

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(3)

(ii) After jumping onto the roundabout platform, the child pushes on a bar in the direction of motion to try to make it go faster. Explain why the speed does not increase.

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(2) (Total 20 marks)

Page 18 of 33

M1. (a) Photon (right-hand box) TO for listing Must state name

Weak (nuclear) / weak interaction / weak nuclear interaction / weak force B1

(left-hand box) TO for listing 2

(b) Charge / (electric) charge B1

TO for listing any other physical quantity Must be word; do not accept symbol

1

(c) Higgs (boson) / Higgs (particle) / Higgs (boson particle) Not graviton

Accept Higg / Higs / Hig

B1 TO for listing

1 [4]

M2. (a) (i) attempt to use F = or E = 14800 (V m1)

C1

F = 2.3 10-15 (N)

C1

acceleration =1.39 (1.4) 1012 m s2

A1 3

Page 19 of 33

(ii) final energy = 3120 eV B1

3120 1.6(1) 1019 = 4.99 or 5.02 J

B1

substitution of their energy in E = 1/2 mv2 with m = 1.67 1027

(condone 1.7) C1

7.677.74 105 m s1 (allow ecf if consistent with their energy

using 2750eV) A1

4

(iii) use of s = (mean v)t or v = u + at C1

33(.4) ns A1

2

B1

B1

B1 3

C1

B = 0.0379

A1

T (tesla) B1

3

(b) (i) Bev =

r =

B, e and m are constant or k =

(ii) 726000 =

Page 20 of 33

(c) as speed increases orbit radius increases B1

the time to go from gap to gap remains the same

B1

in a synchrotron orbit radius is constant

B1

as speed increases B must increase to maintain the constant radius

B1 4

(d) manufacture of radioactive isotopes for use in diagnosis and treatment B1

eg sources do not decay whilst in transit (fresher sources) less risk in transporting radioactive materials by road use a lot of r/a materials so cheaper than buying in sources

B1 2

[21]

M3. (a) time to halve = 0.008 s or two coordinates correct C1

C = T1/2

/(0.69 150) or eg 0.4 = 1.4 e0.015/150C

A1

77 F (consistent with numerical answer) A1

3

Page 21 of 33

(b) max 3 from as capacitor discharges:

pd decreases

B1

current through resistor decreases (since I V) B1

rate at which charge leaves the capacitor decreases (since I = Q/t) B1

rate of change of charge is proportional to rate of change of pd (since V Q)

B1

condone quicker discharge when pd is larger

B1 3

(c) energy stored V 2 or use of CV 2

or initial energy = 78.4 (or 75.5) J or final energy using V = 0.380.4 0 V (answer in range 5.6 6.4 J)

C1

fraction remaining = (0.4/1.4)2 or 0.072 0.081

or energy lost = 72 J

C1

91.8 to 92.8% lost

A1 3

(d) (i) charge = 77 C to 82 C B1

1

Page 22 of 33

(ii) charge required = 77 106 5 3.15 107 (= 12128 C)

or 1Ah =3600 C

C1

3.36(3.4) Ah A1

2 [12]

M4. (a) Calcium = 40, 20 correct order B1

Beta minus = 0, 1 correct order

B1 MAX 2

Top line correct / bottom line correct

B1 2

(b) Same energy released in (each) decay B1

When beta less than max there is missing energy / missing energy cannot be accounted for by recoil of (daughter) nucleus / total energy of beta and recoil nucleus not constant (appears to be violation of conservation of energy)

B1 If only two particles there wouldn't be a range there would be a single value

(Must be another particle) to carry away (missing) energy B1

3 [5]

Page 23 of 33

M5. electrons

M1

high energy scattering/inelastic/KE not conserved

M1

demonstrated substructure of proton

A1 3

[3]

Page 24 of 33

M6. (a) (i) arrow shown left to right between the poles of the magnets B1

(ii) Attempt to use of F = BIL M1

Correct calculation of the force 1.07 105 leading to 30 T

A1 Condone 3 105 (1 sf)

T

B1

(b) Component of B perpendicular to wire decreases M1

Reading falls

A1

Or

Field changes direction / force changes direction

M1

reading would decrease

A1

(c) refers to an object (eg a top / proton spinning axis of rotation also rotates: accept sensible diagram

protons aligned by strong magnetic field produced by a coil Aligning field switched off protons undergo precession around the field present at that point precessing protons induce e.m.f. in a coil measure the frequency of the induced emf mention of Lamor frequency frequency is proportional to the strength of the field reward useful diagrams used in the explanation

B6 5 - 6 Addresses precession and covers alignment of protons / preceesion frequency / induced emf / precession frequency proportional to B 3 - 4 Makes sensible attempt at explaining precession and covers some aspects of the operation of the magnetometer. Likely to appreciate that it is the precession frequency that is measured 1 - 2 Makes some sensible comments in an attempt to explain

Page 25 of 33

precession and / or the operation of the magnetometer [12]

M7. (a) (i) electrons are produced by heating a metal. electrons liberated from the surface or deeper in the metal

or

B1

energy to remove electrons is variable

B1

or

energy supplied for electrons to leave may be greater than the work function

2

(ii) attempt to use eV = mv2 or calculates KE correctly

9.2 1016J

C1

1.6 1019 V = 9.1 1031 (4.5 107)2

C1

or eV = 9.2 1016J (equates eV to correct Ek)

5800 (5759) (5765)(V) A1

3

(b) (i) Into the page M1

applied LHR remembering that electrons are opposite direction to the current

A1 2

Page 26 of 33

C1

or r=mv/Bq

correct substitution ignore errors in powers of 10

C1

0.18(3) (m) A1

3

B1

9.213 (9.21) 1031 (kg) seen

B1

increase in mass = 0.1 or 0.11 1031 kg

B1

or

calculates ratio of new to rest mass (1.011 of rest mass) (Allow even if candidate thinks this is the answer) 1.1(4) %

B1 4

(ii)

(c) (i) New mass = or

Page 27 of 33

(ii) Potential difference: higher OR states answer to (b)(i) is too small

extra energy to increase the mass

or

as mass increases acceleration would decrease unless pd is greater to increase the (average) force (OWTTE)

M0

or

A1

Answers in terms of eV = mv2 stating v constant so V m

Path radius: larger

Larger mass deflected less by same force

or

larger mass requires larger force to produce the same radius of curvature

or

M0

same force acting on larger mass so central acceleration in lower

A1

or

radius is proportional to mv so higher m gives higher r for given v

or

Explanations using equation with constant quantities identified 2

(d) (i) Force required toward A/ A has to attract electrons B1

A has to be positive

B1 2

Page 28 of 33

(ii) eE = Bev or v = E/B

E = 63000 V m1 or algebra leading to V = Bvd

Use of E = V/d or substitution (condone incorrect powers of 10) V = 2210 V

4 [22]

M8. (i) More penetrating than alpha B1

Alpha would have been stopped by metal foil / gas

B1 2

(ii) Alpha = 4,2 correct order B1

X = 1,1

B1 2

(iii) proton B1

1 [5]

M9. (a) (i) Pd / electric field between the dees B1

Exert force on (charged) proton / reference to Eq or Vq/d B1

Pd alternates (so proton is accelerated whichever direction its going in) B1

3

(ii) equates BQv and mv 2/r

B1

involves v = r and T = 2 / or similar in clear and logical analysis

B1 2

Page 29 of 33

(iii) Rearranges to give

C1

1.51(T) A1

2

(b) (i) Particle must stay inside each electrode for the same length of time B1

Particles are travelling faster (towards the right) B1

2

(ii) Particles approaching the speed of light B1

Mass increase + mention of relativity

B1

Acceleration of particle is reduced

B1

Correct reference to relativity equation ANY 3 MAX 3

(iii) Collision used to create new (massive) particles B1

Energy required to produce new matter

B1

More ke in proton-proton collision

B1 3

[15]

M10. (a) Use of cos 20 or sin 70 or F(horizontal) = 30 / 1.3 = 23.1 C1

24.6 (N) 2

OR substitutes into any correct form eg

condone power of ten for f

Page 30 of 33

(b) (i) angular acceleration = T / I C1

30 / 240 = 0.125 rad s2

A1

= 180 or seen

B1

2 = 2 0.125 or 2 = 2

B1 Allow substitution with their and = 180

0.886 (2 or more sf) B1

5

(ii) Use of conservation of angular momentum or use of T = 2 / C1

variations for use of 0.89 and reasonable rounding errors allowed

Initial angular momentum 240 0.9 (allow 212 to 216) (kg m2 s1)

C1

Final angular speed = 0.76 rad s1

A1

8.3 s Allow ecf from incorrect (likely to be 7.0 s or 7.1 s allow 1 sf) B1

4

(iii) Energy = I2

C1

Calculation of one energy correctly 97J or 82 J

C1 Allow 115 J from (240 + 45) 0.92

Calculates both correctly and subtracts (15J) A1

3

Page 31 of 33

(iv) Collision is inelastic B1

or Energy converted into heat / internal energy when child jumps on or work done against friction at contact point when child jumps on

1

(c) (i) acceleration is (rate of change) of velocity B1

velocity is a vector or has (magnitude and) direction B1

direction of (linear motion) is changing B1

or

acceleration = force / mass

B1

there is a force on the child toward the centre of the roundabout

B1 Mention of centripetal force / acceleration

Some discussion of how the force arises(friction or holding on) B1

3

(ii) Mention of Newtons third law or equivalent statement Equal and opposite force on child and roundabout

B1

application to the situation (applying force to the object he is on) B1

or

Child is part of the system

B1

Is not providing an external torque force

B1 2

[20]

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