Physics Paper 2 November 2002

1. ABoth sides reduce to s^-1, so the equation is dimensionally consistent.
2. BThe left side reduces to s^-1 but the right side reduces to m s^-1, so the equation is not dimensionally consistent.
3. CBoth sides reduce to metres, so the equation is dimensionally consistent but physically meaningless.
4. DThe right-hand side is dimensionless, so the equation cannot represent a frequency.

1. A[ρv] works out to kg m^-1 s^-2, exactly matching the units of pressure, so the equation is dimensionally correct as printed.
2. B[ρv] works out to kg m^-2 s^-1, which does not match the units of pressure (kg m^-1 s^-2), so the equation is not dimensionally correct as printed.
3. CPressure has no fixed base units of its own, so no dimensional check can be applied to this equation.
4. D[ρv] works out to kg m^-3 s^-1, which happens to coincidentally match the base units used for density alone rather than pressure, so the equation is still treated here as dimensionally correct.

1. Atanθ is dimensionless, but v²/(rg) reduces to units of m s^-2 once the radius and gravitational acceleration are substituted, so the equation is not dimensionally consistent as printed.
2. Bv²/(rg) reduces to units of seconds, so the equation cannot be dimensionally correct.
3. Ctanθ is dimensionless, and v²/(rg) also reduces to a dimensionless quantity, so the equation is dimensionally consistent.
4. DBoth sides carry units of m s^-1, so the equation happens to be consistent by coincidence.

1. ATorque only exists in rotational systems, and the joule is defined only for translational (straight-line) systems.
2. BTorque is the turning effect of a force at a perpendicular distance, not a transfer of energy, so using the joule would wrongly imply that energy is being transferred.
3. CTorque and energy do not actually share the same base units once expressed in kilograms, metres and seconds, so the joule would be dimensionally the wrong unit for torque entirely, regardless of physical meaning.
4. DThe joule is defined only for electrical quantities, not for mechanical quantities like torque.

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1. Ahorizontal = u sin55°, vertical = u cos55°
2. Bhorizontal = u cos55°, vertical = u cos55°
3. Chorizontal = u sin55°, vertical = u sin55°
4. Dhorizontal = u cos55°, vertical = u sin55°

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1. AThe centre of gravity must lie at the object's geometric centre, and the resultant force is zero.
2. BThe resultant force on the system is zero, and in addition the object must remain completely stationary at all times, never moving even momentarily.
3. CThe resultant (net) force on the system is zero, and the resultant (net) moment about any point is zero.
4. DThe resultant moment is zero, and the object must be accelerating at a constant rate.

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1. AThe rate of change of a force's momentum as it acts about a pivot.
2. BThe product of a force and the perpendicular distance from the pivot to the force's line of action.
3. CThe energy required to rotate an object through one radian about a pivot.
4. DThe product of a force and the distance moved by its point of application, in the direction of the force.

1. AThe wrench is turned while a scale on the wrench indicates the torque currently being applied; turning stops once the scale reads the required value.
2. BThe wrench is turned a fixed number of full rotations, since one rotation always corresponds to a fixed torque regardless of the force applied, making the applied force itself irrelevant to how tight the nut ends up.
3. CThe user times how long the wrench is turned for, since torque is assumed proportional to the turning time.
4. DThe wrench has a spring that releases automatically at a fixed force, independent of the length of the torque arm.

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1. AA longer handle is only for a more comfortable grip; it has no real effect on the torque produced.
2. BA longer torque arm means a smaller applied force is needed to produce the same torque, making it easier to apply a large torque by hand.
3. CA longer handle increases the force applied without changing the torque actually needed to tighten the nut.
4. DA longer handle reduces the torque required to turn the wrench, since torque itself is assumed to decrease as the arm length increases, the opposite of the true relationship between force, arm length and torque.

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1. AIt is dissipated as heat, mainly due to friction between the threads of the nut and bolt and other contacting surfaces.
2. BIt is converted into sound energy as the wrench clicks and the nut settles into place.
3. CIt is transferred into the torque wrench's own internal spring mechanism for later reuse.
4. DIt is stored as additional elastic potential energy in the bolt, beyond the initial 1.5 mm stretch already accounted for.

1. AThe change in direction of a wave as it passes from one medium into another of different density.
2. BThe superposition of two waves travelling in opposite directions to form a standing wave pattern.
3. CThe spreading (bending) of waves as they pass through a gap or around the edge of an obstacle.
4. DThe gradual decrease in a wave's amplitude as it travels further from its source.

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1. APattern A
2. BPattern B
3. CBoth patterns equally
4. DNeither pattern

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1. AIn A the wavefronts emerge as almost complete semicircles, showing strong diffraction from a gap comparable in width to the wavelength; in B the wavefronts stay largely straight, showing weaker diffraction from a wider gap.
2. BIn A the wavefronts appear to travel measurably faster after emerging from the gap than they did on the approach side, and this apparent speed increase is assumed here to occur only when the gap the wave passes through is very narrow.
3. CIn A the wavelength of the wave increases after passing through the gap, a change that is unique to narrow gaps.
4. DIn A the wave amplitude is measurably higher after the gap than in B, which indicates the narrower gap width.

1. ALight waves do not diffract at all under any circumstances, because their electric and magnetic field components are assumed here to force them to always travel in perfectly straight lines, with no bending around any obstacle or through any gap however narrow.
2. BSound travels more slowly than light, and only slower-moving waves are able to diffract around an obstacle.
3. CSound waves are transverse while light waves are longitudinal, and only longitudinal waves diffract to a noticeable extent.
4. DSound wavelengths (millimetres to several metres) are comparable to the size of everyday gaps and obstacles, so sound diffracts noticeably; light's much shorter wavelength (about 5×10^-7 m) needs an extremely narrow slit to show noticeable diffraction.

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1. AFleming's right-hand rule: First finger = Field, seCond finger = force, thuMb = Current, a mnemonic actually used for predicting induced e.m.f. rather than motor force.
2. BLenz's law: the induced force always opposes the change in the current that produces it.
3. CFleming's left-hand rule: First finger = Field, seCond finger = Current, thuMb = force/Motion.
4. DThe right-hand grip rule, applied directly to the current direction in the conductor.

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1. AThe rails heat up unevenly along their length, causing thermal expansion; this is addressed by water-cooling the rails during use.
2. BThe magnetic field between the rails cancels to zero, stopping the slug from accelerating; this is addressed by reversing the current direction periodically.
3. CThe anti-parallel currents make the two rails repel each other, which can bow or misalign them over repeated use; this is addressed by mounting the rails on a rigid, braced support structure.
4. DThe anti-parallel currents make the two rails attract each other, risking a short circuit between the rails and the sliding conductor; this is addressed in this option by simply spacing the two rails further apart from one another.

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1. A4 V (using only the p.d. across the ohmic conductor P).
2. B10 V (reading off the highest voltage value shown on the graph's axis).
3. C2 V (using only the estimated p.d. across the non-ohmic conductor Q, and ignoring the separate contribution from the ohmic conductor P entirely).
4. D6 V (reading V≈4V across P and V≈2V across Q at I=0.2A, then summing the two since P and Q are in series).

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1. A0.35 A (only the current through the non-ohmic conductor Q, ignoring the current through P).
2. B1.0 A (mistakenly reading the currents for both conductors at V=10V on the graph's axis, instead of at the actual 6V supply voltage found earlier).
3. C0.30 A (only the current through the ohmic conductor P, ignoring the current through Q).
4. D0.65 A (I≈0.3A through the ohmic conductor P at 6V, plus I≈0.35A read from the graph for Q at 6V, summed since P and Q are in parallel).

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1. AThermometers only agree with each other if they are made from exactly the same material.
2. BDifferent thermometers rely on different thermometric properties (e.g. liquid expansion, resistance, e.m.f.) that do not all vary identically with temperature except at the fixed calibration points.
3. CDisagreement between thermometer types is caused only by random manufacturing errors in each device.
4. DEvery thermometer type is calibrated against a different assumed value of absolute zero on its own internal scale, so their readings can never be made to agree with one another under any conditions.

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1. AA blackened surface is assumed here to reflect thermal radiation more effectively than a shiny one would, giving a steadier and more stable temperature reading over the course of the experiment.
2. BBlackening increases the thermal conductivity of the metal disc, speeding up the conduction of heat through it.
3. CBlackening is done purely for visibility, to mark the disc's position underneath the dome.
4. DA blackened (matt black) surface is a good absorber and a good emitter of thermal radiation, maximising the radiant energy transferred and minimising reflection.

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