Practice Paper 2 (HL IB Physics)

Part of a delivery system in a factory consists of a freely rotating cylinder attached to a central shaft that sits on top of rails. The cylinder has a mass of 0.60 kg and the central shaft a mass of 0.30 kg. The radius of the central shaft is 1.5 cm and the radius of the cylinder is 5.0 cm. The cylinder and the central shaft have a linear velocity of 10 m s⁻¹.

Calculate the angular velocity of the central shaft and the cylinder. 

Explain why the central shaft and the cylinder are travelling at the same linear velocity but different angular velocities. 

The central shaft can be modelled as a cylinder that passes through the hollow centre of the cylinder. 

Moment of inertia of a solid cylinder, 

Moment of inertia of a hollow cylinder,  where A is the radius of the hollow and B is the radius of the outer part.

Calculate the moment of inertia of the central shaft and cylinder. 

Water at constant pressure boils at a constant temperature.

Outline the reason for this, in terms of the energy of the molecules.

In an experiment to measure the specific latent heat of vaporization of water, steam at 100°C was passed into water in an insulated container.

The following data are available.

• Initial mass of water in container = 0.260 kg
• Final mass of water in container = 0.278 kg
• Initial temperature of water in container = 20.4 °C
• Final temperature of water in container = 53.4 °C
• Specific heat capacity of water = 4.18 × 10³ J kg^–1 K^–1

Show that the specific latent heat of vaporization of water is about 1.8 × 10⁶ J kg^–1.

The diagram shows a battery of e.m.f. 40.0 V and internal resistance, r.

The current in the battery is 2.5 A. 

Calculate the internal resistance r.

Calculate the energy dissipated in the battery in 3.5 minutes.

The circuit is amended to include a solar cell. 

Explain the function of a solar cell and an advantage it has in an electric circuit over a chemical cell.

The internal resistance of the cell affects the efficiency of the transfer of energy from the cell to the circuit. 

Explain what causes internal resistance and why this affects the efficiency of the cell.

The diagram shows a stationary wave source, R, in water. The source produces waves with a constant frequency. The distance between each successive wavefront is equal to the wavelength of the waves produced by R.

The speed of the waves in water is v.

Sketch three successive wavefronts produced when the source is moving to the right at a speed of 0.75v. 

A scientist sits on a boat to the right of the source and measures the frequency of the waves as they approach.

Explain the observations the scientist will make.

The speed of the waves is 2.5 m s⁻¹. The wavelength of the waves as emitted by the source is 3.45 m. 

Calculate the frequency of the waves as observed by the stationary boat.

Four point charges A, B, C and D are each placed at a distance d from O as shown below.

A has a charge –q and B, C and D each have a charge +q­.

Write an expression for the magnitude of the resultant electric field strength at O in terms of q and d.

The arrangement of the charges is changed to the grid shown below. Each charge is now the corner of a square of side x, where x = 2d.

Write an expression for the magnitude of the resultant electric field strength at point O in terms of q and d.

An alpha particle with an initial speed one-tenth that of the speed of light is fired head-on at a stationary gold nucleus .

Calculate the minimum separation between the alpha particle and the centre of the gold nucleus.

When monochromatic light is incident on a clean metal surface, photoelectrons may be emitted through the photoelectric effect.

Explain why, although the incident light is monochromatic, the kinetic energies of emitted photoelectrons vary up to some maximum.

Explain why no photoelectrons are emitted if the frequency of the incident light is less than a certain value, no matter how intense the light. 

For monochromatic light of wavelength 570 nm a stopping potential of 1.80 V is required for this particular metal surface. 

Determine the minimum energy required to emit a photoelectron from the metal surface. 

When scientists develop climate models for planets other than Earth, the value of the solar constant  must be adjusted.

Explain why is a constant and how it can be adjusted for different planets in the Solar System.

Different climate models consider the energy absorbed by the Earth with and without an atmosphere.

Explain why the average power absorbed per unit area of the Earth is less than in both models.

A simplified energy balance model of the Earth with an atmosphere is shown in the diagram.

In this model, the Earth's surface is assumed to be a black body radiator at constant temperature . It receives both solar radiation and radiation emitted from the atmosphere. The atmosphere is modelled as a body with albedo and average equilibrium temperature .

Determine the value of  used in this model.

Calculate the average equilibrium temperature of the Earth's surface . 

Carbon dioxide and water vapour are both known to be greenhouse gases.

Compare and contrast the roles of carbon dioxide and water vapour in the greenhouse effect. 

Suggest why the burning of fossil fuels may lead to an increase in global warming by the enhanced greenhouse effect.

A generator in a hydroelectric plant features a coil rotating in a magnetic field with a constant angular velocity.  

The power output of the generator varies over time and supplies a maximum power output of 6 kW at 50 A when rotating at a frequency of 20 Hz.

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Using Faraday's Law, show that the new power output is 96 kW if the frequency of the rotation of the coil increases to 80 Hz.

You may use the following equation

A graph showing the variation in power over time for a different hydroelectric generator is shown below. 

In this generator, when the rate of flow of water from the dam doubles, the frequency of revolution of the coil also doubles.

On the diagram above, sketch a curve showing the new variation in power over time when the flow rate halves.

The braking system of the hydroelectric generator also utilises electromagnetic induction.

The components of the electromagnetic braking system are shown in the diagram. A metal disc is attached to the rotating axle of a vehicle. An electromagnet is mounted with its pole pieces placed on either side of the rotating disc, but not touching it. 

When the brakes are applied, a direct current is passed through the coil of the electromagnet and the disc slows down.

Explain, with reference to appropriate laws of electromagnetic induction, how this design can produce a braking effect.

A conventional braking system has friction pads that are brought into contact with a moving metal surface when the vehicle is to be slowed down. 

Suggest one advantage and one disadvantage of an electromagnetic brake compared to a conventional brake.

The principle of mutual induction is used in the transmission of alternating current from a hydroelectric power plant. An arrangement of coils in two separate circuits, P and Q, is shown in the diagram.

When the switch is closed there is a current in the coil in circuit P. The current is in a clockwise direction as viewed from position O. Circuit Q is also viewed from position O. 

Outline how Lenz’s law predicts the direction of the induced current when the switch is opened and again when it is closed.