AQA A Level Physics Paper 2 June 2024 question paper 7408/2

A room contains dry air at a temperature of 20.0 °C and a pressure of 105 kPa.

Show that the amount of air in each cubic metre is about 40 mol.

The density of the dry air is 1.25 kg m⁻³.

Calculate c_rms for the air molecules. Give your answer to an appropriate number of significant figures.

Calculate, in K, the change of temperature that will double c_rms for the air molecules.

A room contains moist air at a temperature of 20 °C. A dehumidifier cools and then condenses water vapour from the moist air. The final temperature of the liquid water that collects in the dehumidifier is 10 °C. Drier air leaves the dehumidifier at a temperature of 20 °C.

Table 1 compares the air flowing into and out from the dehumidifier.

In one hour, a volume of 960 m³ of air flows through the dehumidifier. Assume that the density of the air remains constant at 1.25 kg m⁻³.

Determine how much heat energy is removed in one hour from the water vapour by the dehumidifier.

specific heat capacity of water vapour = 1860 J kg⁻¹ K⁻¹ specific latent heat of vaporisation of water = 2.3 × 10⁶ J kg⁻¹

Figure 1 shows a circuit used to charge capacitor C. The battery has negligible internal resistance.

The capacitance of C is known.

The switch is closed at time t = 0 and the potential difference V_C across C is recorded at different times t. Figure 2 shows the variation of V_C with t.

Explain how a gradient of the graph in Figure 2 can be used to determine the initial

The potential difference V_R across R is also recorded. Figure 3 shows the variation of V_R with t between t = 20 s and t = 45 s.

The capacitance of C is 31.0 μF.

Determine, using Figure 3, the time constant of the circuit. Go on to show that the resistance of R is about 2.4 × 10⁵ Ω.

The current I₀ at time t = 0 is 3.6 × 10⁻⁵ A.

Determine the time at which V_C is 6.0 V.

A conducting rod is held horizontally in an east–west direction. The magnetic flux density of the Earth’s magnetic field is 4.9 × 10⁻⁵ T and is directed at an angle of 68° to the ground.

Figure 5 shows the arrangement. The rod has a length of 2.0 m.

The rod is released and falls 8.0 m to the ground. It remains in a horizontal east–west direction as it falls.

Determine the average emf across the rod during its fall to the ground. Assume that air resistance is negligible.

The rod is returned to its original position. It is now supported by a non-conducting pole that is hinged on the ground as shown in Figure 6. The pole is initially vertical and is then released. The rod and pole can fall to the ground to the left or to the right.

During each fall there are changes in the magnitude and direction of the induced emf. These changes differ depending on whether the rod falls to the left or to the right.

Explain any changes in the magnitude and direction of the induced emf as the rod falls:

• to the left

• to the right.

One purpose of the coolant in a thermal nuclear reactor is to maintain a safe working temperature within the core.

State the other purpose.

State two properties that engineers consider when choosing a liquid to use as a coolant in a thermal nuclear reactor.

Explain how the power output of a thermal nuclear reactor is decreased.

A satellite S₁ is placed in a circular orbit around the Earth so that observations of the far side of the Moon can be made continuously.

S₁ has the same angular speed as the Moon so that the centres of the Earth, the Moon and S₁ are always in a straight line.

Figure 7 shows two positions of the Moon and S₁ as they orbit the Earth.

The resultant force on S₁ is due to the gravitational forces from the Earth and the Moon. The magnitude of the Earth’s gravitational field strength at the orbital radius

The magnitude of the Moon’s gravitational field strength at the orbital radius

Show that g_M is approximately 1.2 × 10⁻³ N kg⁻¹.

period of the Moon’s orbit = 27.3 days

Calculate the distance from S₁ to the centre of the Moon.

Another satellite S₂ is placed in a circular orbit between the Earth and the Moon. S₂ always views the near side of the Moon. S₂ also has the same angular speed as the Moon so that the centres of the Earth, the Moon and S₂ are always in a straight line. Figure 8 shows two positions of the Moon and S₂ as they orbit the Earth.

Explain how the resultant force on S₂ due to the gravitational fields of the Earth and the Moon causes S₂ to orbit with the same angular speed as the Moon. No calculations are required.

The electric potential at a point in an electric field is −4.0 V.

Explain what is meant by this statement.

Figure 9 shows an arrangement for confining groups of electrons to small regions inside a block of gallium arsenide.

Electrons can only move along the line PQ in the block.

When a suitable electric potential is applied to the electrodes, the electrons are confined to the regions shown in Figure 9.

The graph in Figure 9 shows how the electric potential V varies with

Determine, using the graph in Figure 9, the maximum magnitude of the electric field. State an appropriate unit for your answer.

An electron at rest at x = 300 nm gains kinetic energy and moves to x = 800 nm.

Determine the minimum kinetic energy required by the electron.

One of the confined electrons is at x = 350 nm.

Discuss the subsequent motion of this electron due to the variation in electric potential shown in Figure 9. Assume that the electron starts from rest.

A team of students uses 900 dice, each with n sides, to model the decay of a radioactive material. Each dice represents a single undecayed nucleus. A throw of the dice represents a constant time interval.

When the dice are thrown, those that show a 1 represent decayed nuclei and are removed. The students count the number N of ‘undecayed’ dice that remain. The procedure is repeated using the undecayed dice.

Figure 10 shows the students’ data.

Explain why N has been plotted on a logarithmic scale in Figure 10.

In this experiment, a decay constant λ can be defined that models the radioactive decay constant.

Determine λ. Go on to use your value for λ to show that n = 4 for the dice used in this experiment.

A typical radioactive source used in schools has an activity of 100 kBq. A radioactive source used in a hospital has an activity of 370 GBq.

State one safety measure when using a radioactive source in a school laboratory. Go on to discuss how this safety measure needs to be adapted for safe use of the hospital radioactive source.

X-rays are a form of ionising radiation.

A person has check-ups with a dentist every six months. The dentist only takes X-ray images when the person has reported a problem.

Suggest why.

In which process is work done by an ideal gas?

Three molecules have speeds 2.00 v, 4.00 v and 5.00 v.

What is the c_rms speed of these molecules?

An ideal gas is enclosed in an insulated container with a small electric heater. The initial temperature of the gas is 300 K. The product of pressure and volume is 5000 J. The gas expands at constant pressure and does 1660 J of work.

What is the final temperature of the gas?

An air-filled parallel-plate capacitor and a resistor are connected in series across the terminals of a battery. The plates of the capacitor are then moved further apart.

This change results in

Which change will increase the efficiency of a transformer?

A signal generator supplies a sinusoidal root mean square voltage of 7.0 V. The sinusoidal voltage is displayed on an oscilloscope screen. The screen has eight vertical divisions.

Which volts/division setting will display the tallest complete waveform?

Two signals that have the same frequency are displayed simultaneously on an oscilloscope. The display is shown with the time-base set to 5 ms div⁻¹.

Which row shows the frequency of both signals and the phase difference between them?

A transmission cable consists of many strands of wire. Electrical energy is transmitted along the cable at a frequency of 50 Hz.

Which change gives the largest increase in the efficiency of the electrical energy transfer along the cable?

An electron enters a uniform magnetic field at right angles to the field. The flux density of the field is B. The electron moves with a non-relativistic speed v in a circular path of radius r.

What is the number of circuits completed by the electron in one second?

The following reaction occurs when a proton and a carbon-13 13C 6 nucleus fuse. 13 1 14

mass of 13 6C nucleus = 13.00007 u

mass of 14 7 N nucleus = 13.99925 u

mass of proton = 1.00728 u

What is the quantity of energy released?

The equation represents a typical fission reaction.

235 1 87 146 1

Which statement about this reaction is not true?

5.6 kW h of heat energy is released when 1.0 kg of wood pellets are burnt in a power station.

What is the mass lost in burning 1.0 kg of wood pellets?

The nuclear radius of an element with nucleon number x is r.

What is the nuclear radius of an element with nucleon number y ?

A synchronous orbit of the Earth has a radius R. A planet has a mass twice the mass of the Earth. A day on the planet is one quarter of an Earth day.

What is the radius of a synchronous orbit for this planet?

An asteroid has a mass of 2 × 10¹⁷ kg and an escape velocity of 40 m s⁻¹.

What is the order of magnitude of the radius of the asteroid?

The diagram shows the gravitational field for a binary star system consisting of two stars X and Y of equal mass.

Equipotential lines are shown as solid lines. Gravitational field lines are shown as dashed lines.

Which statement is correct?

Which is equal to ε₀?

The force between two point charges is F. The magnitude of each charge is doubled and the distance between them is halved.

What is the new force between the two charges?

Which diagram shows a distribution of charge where the electric potential at P and the electric field at P are both zero?

An ion has a specific charge of −7.1 × 10⁷ C kg⁻¹. It is held stationary in a vertical electric field on the surface of the Earth.

What are the magnitude and direction of the electric field?

the same distance?

What can be deduced about the radius r of a nucleus of gold from the scattering of alpha particles by gold nuclei?

The graph shows a plot of neutron number N against proton number Z for the known atomic nuclei.

The nuclide 115 45Rh is likely to decay by

Uranium-238 absorbs a neutron in the first stage in a series of nuclear reactions that end in a nucleus Z.

238

How many neutrons does Z have?

A rock sample is found to contain the stable isotope lead-207. When it was formed, the rock contained uranium-235 but did not contain any lead-207.

Uranium-235 decays by a series of steps into lead-207. The half-life of uranium-235 is 0.71 billion years. The half-lives of the nuclides in the intermediate steps are negligible.

The sample of rock now contains one atom of lead-207 for every four atoms of uranium-235.

How long ago was the rock formed?