Paper 4 for A2 Final Term 2065

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1. The diagram shows a gymnast of weight 720N hanging centrally from two rings, each attached to cables which hang vertically.

The center of mass of the person was at a height of 2m from the ground level. a. Calculate the skydiver’s gravitational potential energy,

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b. The diagram shows the gymnast after he has raised his body so that his centre of mass moves through a vertical distance of 0.50 m.

Calculate the skydiver’s gravitational potential energy after this maneuver,

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c. The gymnast has to drop to the ground ultimately in both cases. Find the difference in the kinetic energy during landing in the two cases.

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2. Define specific latent heat of fusion.

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Some crushed ice at 00C is placed in a funnel together with an electric heater, as shown in the fig.

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The mass of water collected in the beaker in a measured interval of time is determined with the heater switched off. The mass is then found with the heater switched on. The energy supplied to the heater is also measured. For both measurements of the mass, water is not collected until melting occurs at a constant rate. The data are obtained as follows:

Mass of water / gEnergy supplied to

heater / JTime interval / min

heater switched off 16.6 0 10.0

heater switched on 64.7 18000 5.0

a. State why the mass of water is determined with the heater switched off.

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b. Suggest how it can be determined that the ice is melting at a constant rate.

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c. Calculate a value for the specific latent heat of fusion of ice.

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3. The needle of a sewing machine is made to oscillate vertically through a total distance of 22mm, as shown in the figure.

The oscillations are simple harmonic with a frequency of 4.5Hz. The cloth that is being sewn is positioned 8.0mm below the point of the needle when the needle is at its maximum height.

a. State what is meant by simple harmonic motion.

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b. Calculate, for the tip of the needle,

i. its maximum speed,

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ii. its maximum acceleration,

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iii. its speed as it moves downwards through the cloth.

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4. Electrons are moving in vacuum with a velocity of and enter a region of uniform magnetic field of value 0.1 tesla as shown in the figure forming an angle of 900.

a. Determine the value of force experienced by the electrons.

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b. Determine the value of the radius of the curve taken by the electron inside the magnetic field.

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c. Draw the prospective path covered by the electrons inside the magnetic field and after leaving the field in the following figure.

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d. Had it been the protons which have been incident, draw the path of the protons inside the magnetic field and after leaving the field, paying special focus to direction and curvature.

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5. A simple iron-cored transformer is illustrated in the figure.

a. Give reason for the core being a continuous loop.

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b. Give reason for the core being laminated.

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c. State Faraday's law of electromagnetic induction.

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d. Use Faraday's law to explain the operation of the transformer.

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e. State two advantages of the use of alternating voltages for the transmission and use of electrical energy.

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6. An isolated conducting sphere of radius ‘r’ is placed in air. It is given a charge +Q. This charge may be assumed to act as a point charge situated at the centre of the sphere.

a. Define electric field strength.

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b. State a formula for the electric field strength ‘E’ at the surface of the sphere. Also, state the meaning of any other symbols used.

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c. The maximum field strength at the surface of the sphere before electrical breakdown (sparking) occurs is 2.0×106Vm-1. The sphere has a radius ‘r’ of 0.35m. Calculate the maximum values of

i. the charge that can be stored on the sphere,

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ii. the potential at the surface of the sphere.

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d. Suggest the effect of the electric field on a single atom near the sphere's surface as electrical breakdown of the air occurs.

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7. Three electron energy levels in atomic hydrogen are represented in the figure.

The wavelengths of the spectral lines produced by electron transitions between these three energy levels are 486nm, 656nm and 1880nm.

a. On the figure, draw arrows to show the electron transitions between the energy levels that would give rise to these wavelengths. Label each arrow with the wavelength of the emitted photon. [3]

b. Calculate the maximum change in energy of an electron when making transitions between these levels.

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