Physics 0625 | Paper 1 Mock 01 | Multiple Choice (Core)

The rising air over the sea is replaced by Cooler air flowing out from the land. At night the land cools faster than the sea, so the air over the warmer sea rises; cooler, denser air over the land then flows out to the sea at ground level to replace it, giving a land breeze. No replacement being needed, or warm air flowing from the land, would break the circulation, since air must move in to fill the gap left by the rising air.

The correct answer is that particles at the hot end vibrate more strongly and pass energy to neighbouring particles. In a non-metal solid the particles are fixed in place by bonds, so heating makes them vibrate harder and they hand kinetic energy on to their neighbours down the rod. Convection cannot happen because the particles cannot flow, they do not leave their fixed positions, and a non-metal has no free electrons to carry the energy.

Evaporation rate increases with both higher temperature and greater air movement across the liquid surface. The dish at 40 °C with air blown across it combines both favourable conditions, so it loses water fastest.

A higher temperature means water molecules at the surface have more kinetic energy on average, so a greater fraction of them have enough energy to escape the liquid. Air blown across the surface carries away the escaped water vapour, preventing a saturated layer from building up just above the liquid. This keeps the concentration gradient steep and allows further molecules to leave.

The dish at 20 °C with no air movement has neither advantage, so it evaporates slowest. The other two dishes each have only one of the two factors, placing them between the extremes.

The correct answer is the time taken for one complete oscillation. The period of a pendulum is defined as the time for one full swing out and back to the starting position. The distance the bob moves describes amplitude, the number of swings per second is the frequency, and the length of the string is a separate quantity that affects the period but is not the period itself.

The gas at the lower pressure is gas P. In a manometer the mercury is pushed down on the high-pressure side and rises on the low-pressure side; since the mercury stands higher on the P side, P is pushing less hard than Q. So Q is at the higher pressure and P the lower. The pressures are clearly not equal (the levels differ by \(h\)) and they can be compared directly from that difference.

The correct answer is C. Kinetic energy \( E_k = \tfrac{1}{2}mv^2 \), so speed counts twice over: A gives \( \tfrac{1}{2}(2)(4^2)=16\ \text{J} \), B \( \tfrac{1}{2}(4)(2^2)=8\ \text{J} \), C \( \tfrac{1}{2}(1)(6^2)=18\ \text{J} \), D \( \tfrac{1}{2}(3)(3^2)=13.5\ \text{J} \). C is largest because its high speed is squared.

Choosing the heaviest trolley (B) ignores that speed, not mass, dominates through the \(v^2\) term.

The correct answer is that energy is carried mainly by free electrons moving through the metal. Copper's free electrons move quickly and transfer kinetic energy from the hot region to the cool region, which is why metals conduct so well. Conduction is not radiation, convection cannot occur in a rigid solid where particles cannot flow, and a metal certainly does contain free electrons, so the other statements are false.

The correct answer is the liquid that remains tends to cool below its surroundings. During evaporation the most energetic particles escape from the surface, lowering the average kinetic energy of those left behind. This causes the remaining liquid to cool below the surrounding temperature. Evaporation does not require the boiling point to be reached, does not keep the temperature constant (that is a feature of boiling), and does not produce bubbles throughout the liquid.

The pull of the string must be larger. The centripetal force needed rises with speed for a fixed radius (\( F = \dfrac{mv^2}{r} \)), so moving faster around the same circle needs a bigger inward pull from the string. It cannot stay the same, because a faster ball requires more force to keep turning; it must not become smaller, which would let the ball fly outward; and it must still point inward, not outward, since the force is always towards the centre.

The correct answer is the speed of the light changes. Light bends (refracts) at the boundary between two media because it travels at different speeds in each medium. Water is optically denser than air, so light slows down and bends towards the normal. The light is refracted, not reflected. Its colour and frequency remain unchanged during refraction; only its speed and wavelength change.

Specific heat capacity tells you how much energy 1 kg of a material needs to rise by 1 °C. The higher the specific heat capacity, the more energy is required for the same temperature change.

From the table, water has a specific heat capacity of 4200 J/(kg °C), which is far higher than aluminium (900), iron (450), or copper (400). For 1 kg heated by 1 °C, water needs 4200 J while copper needs only 400 J.

This is a direct reading of the definition: the material with the largest specific heat capacity value requires the most energy per kilogram per degree.

Correct answer: They gain kinetic energy at the hot end and carry it as they move toward the cooler end

Correct answer: Because the particles are locked in fixed places and cannot flow to carry energy

The correct answer is A. A gas is easily compressed because of the large spaces between its particles, so the sample whose volume changes by a large amount when squeezed, sample A, is the gas. Samples B and C change volume by almost nothing, meaning their particles are already close together (a liquid or solid), so neither is the gas.

The correct answer is 5 Hz. Frequency is the number of complete waves per second: \( f = \frac{\text{number of waves}}{\text{time}} = \frac{15}{3} = 5\,\text{Hz} \). Multiplying instead of dividing gives 45 Hz. Choosing 3 Hz confuses the time with the frequency.

The correct answer is that a shiny, polished surface is a poor absorber and a good reflector of radiation. The arrows show most of the incoming radiation bouncing off rather than being absorbed, which is exactly how a polished silver surface behaves. Radiation is not conducted, and a shiny surface is also a poor emitter, not a good one, so it neither absorbs strongly nor radiates strongly.

Gravitational field strength \(g\) is defined by the equation \(g = W/m\), where \(W\) is weight measured in newtons (N) and \(m\) is mass measured in kilograms (kg). To find the unit of \(g\), substitute the units into the equation:

\[ \text{unit of } g = \frac{\text{unit of } W}{\text{unit of } m} = \frac{\text{N}}{\text{kg}} = \text{N/kg} \]

This tells you that for every kilogram of mass, there is a certain number of newtons of gravitational force. On Earth's surface, \(g \approx 10\) N/kg, meaning every kilogram of mass experiences about 10 N of gravitational pull.

The correct answer is the ball on the steel rod. Steel is the poorest conductor of the four metals, so energy travels along it most slowly and its wax takes longest to soften, making its ball the last to drop. Copper is the best conductor and its ball falls first, with brass and iron falling before steel.

The correct answer is 15 J, mostly as thermal energy. By conservation of energy, wasted energy = input - useful output = \( 60 - 45 = 15 \, \text{J} \). In an electric motor, friction in the bearings and resistance in the coils dissipate the wasted energy mainly as thermal energy (heat). 105 J would exceed the input, and sound or chemical energy are not the main waste forms in a motor.

The correct answer is that the pressure increases. Water pressure grows with depth according to \( p = \rho g h \), so the deeper the diver goes the larger h and the greater the pressure. It does not decrease or stay the same, and it rises steadily rather than first falling then rising, so the other options are wrong.

A thermal is a rising column of warm, less dense air (a convection current). Ground warmed by the Sun heats the air above it, which expands, becomes less dense and rises as a column, and a glider circling in it is carried upward. It is not a conduction current or a downward flow of cold air, and it is a movement of air, not a beam of radiation.

The correct answer is wave 2. Frequency equals the number of waves divided by the time: wave 1 = 10/5 = 2 Hz, wave 2 = 20/4 = 5 Hz, wave 3 = 12/6 = 2 Hz, wave 4 = 9/3 = 3 Hz. Wave 2 at 5 Hz has the greatest frequency.

The correct answer is 10 000 W. First find the kinetic energy gained: \( KE = \tfrac{1}{2}mv^{2} = \tfrac{1}{2} \times 1000 \times 10^{2} = 50\,000 \) J. Then average power is \( P = \frac{E}{t} = \frac{50\,000}{5} = 10\,000 \) W. Choosing 50 000 W forgets to divide by time; 2000 W uses \( mv/t \) without the half; 5000 W halves the correct answer again.

The acceleration is 2.5 m/s\(^2\). From \( F = ma \), \( a = \dfrac{F}{m} = \dfrac{5000}{2000} = 2.5\ \text{m/s}^2 \). The value 0.4 m/s\(^2\) inverts the fraction \( \left( \tfrac{2000}{5000} \right) \), 2500 m/s\(^2\) and 400 m/s\(^2\) come from misplacing the decimal or multiplying, so only \( \tfrac{5000}{2000} \) gives the correct 2.5 m/s\(^2\).

The correct answer is 1.5 m/s. With 50 dots per second each gap takes \(\frac{1}{50}=0.02\ \text{s}\), and each gap is 3 cm \(=0.03\) m, so speed \(=\frac{0.03}{0.02}=1.5\ \text{m/s}\). 15 m/s and 150 m/s come from unit-conversion slips, and 0.6 m/s divides the wrong way.

The correct answer is that it reduces energy loss by convection, by stopping warm air escaping and cold air entering. The gap under a door lets warm room air leave and cold outside air flow in, a convection exchange, and the brush seals that gap. Cooling the door would be conduction, reflecting radiation describes a shiny foil, and evaporation from the walls is not involved.

The correct answer is C (7.9 g/cm³). Water pushed out of a full displacement can equals the object's volume, so \( V = 6\ \text{cm}^3 \) and \( \rho = \frac{47.4}{6} = 7.9\ \text{g/cm}^3 \). Dividing volume by mass gives the inverted 0.13, while 2.9 and 8.9 do not follow from \( m/V \).

The spring stretched beyond its limit of proportionality is the one whose line starts straight and then curves (labelled B in the figure). Up to the limit of proportionality the force-extension graph is a straight line through the origin; past that point extra load produces disproportionately more extension, so the line bends away from the straight part. The fully straight graphs stay within the limit of proportionality, and the flat horizontal graph shows extension with no increase in force, neither of which is the curving-beyond-the-limit behaviour asked for.

Satellite communication links use microwaves. Microwaves have frequencies high enough to carry large amounts of data and, crucially, they can pass through the Earth's atmosphere (including clouds and rain) with relatively little absorption, making them ideal for ground-to-satellite transmissions.

Radio waves can also pass through the atmosphere but are generally used for different purposes (broadcast radio, TV); the specific application of a dish-to-satellite-to-dish link as shown in the diagram is the classic microwave scenario at IGCSE level. Ultraviolet and infra-red would be heavily absorbed or scattered by the atmosphere, making them unsuitable for this purpose.

The correct answer is a micrometer screw gauge. A micrometer measures to 0.01 mm, making it the most suitable for the small diameter of a thin wire. A metre rule (1 mm divisions) is far too imprecise, a stopwatch measures time not length, and a measuring cylinder measures volume.

Correct answer: 34°

A substance is a liquid at a given temperature only if that temperature is above its melting point but below its boiling point.

At 20 °C, mercury qualifies because its melting point is −39 °C (below 20) and its boiling point is 357 °C (above 20), so 20 °C lies within its liquid range.

Sodium melts at 98 °C, so at 20 °C it is still solid; nitrogen (boiling point −196 °C) and oxygen (boiling point −183 °C) have already boiled to gas well below 20 °C, so none of those is liquid at room temperature.

The rate at which an object emits thermal radiation increases with its temperature. The hotter an object is, the more infrared radiation it emits per second. Since the bar at 600 °C is at a much higher temperature than the bar at 300 °C, it radiates energy at a significantly greater rate.

In fact, the rate of radiation is proportional to the fourth power of the absolute temperature (the Stefan-Boltzmann law), so even a moderate increase in temperature produces a dramatic increase in radiation output. Both bars have identical surfaces and dimensions, so the only variable is temperature. The diagram illustrates this by showing more radiation waves leaving the hotter bar. Neither bar stops emitting radiation at any temperature above absolute zero.

Correct answer: Radiation

Convection cannot happen in a solid because The particles are fixed in place and cannot flow to carry energy. Convection needs a fluid whose particles can move bodily, carrying their energy with them; in a solid the particles only vibrate about fixed positions, so no current can form. Solids do contain thermal energy and are not always the coldest state, and free electrons relate to conduction, not convection.

The correct answer is 1.0 × 10¹⁰ Hz. Using \( f = \frac{v}{\lambda} = \frac{3.0 \times 10^8}{0.030} = 1.0 \times 10^{10}\ \text{Hz} \), with the wavelength converted from 3.0 cm to 0.030 m. \( 1.0 \times 10^9 \) Hz comes from forgetting the cm-to-m conversion, and the two smaller answers divide the wrong quantities.

With the heater near the top, Only the upper water gets hot; the lower water stays cold. Warm water is less dense and stays where it is made, so no convection current forms to carry energy downward; the cold water below cannot rise. Because water is a poor conductor, very little energy reaches the bottom, so the tank does not heat evenly.

The correct answer is convection. The hot gases above the fire are less dense than the surrounding cooler air, so they rise and carry the smoke up the chimney as a convection current in the fluid. Conduction and radiation do not involve bulk movement of the gas, and evaporation is a change of state of a liquid, not the process lifting the smoke.

The data in the table show a linear pattern: every additional 3 N of force produces an additional 2.0 cm of extension. This means the spring constant is:

\[ k = \frac{F}{x} = \frac{3}{2.0} = 1.5 \text{ N/cm} \]

Since the spring obeys Hooke's law, this ratio remains constant. To find the force that produces 8.0 cm of extension:

\[ F = k \times x = 1.5 \times 8.0 = 12 \text{ N} \]

Alternatively, you can extend the pattern in the table: 3 N gives 2.0 cm, 6 N gives 4.0 cm, 9 N gives 6.0 cm, so 12 N gives 8.0 cm. Each step adds 3 N for every 2.0 cm. The key principle is that under Hooke's law, force and extension are directly proportional, so you can scale up using the same ratio.

The pitch of a sound is determined by its frequency: a higher frequency means a higher pitch. On an oscilloscope, frequency is visible as the number of complete cycles that fit into a given horizontal distance. A wave with more cycles packed into the same screen width has a shorter period and therefore a higher frequency.

Examining the four traces (all recorded with the same oscilloscope settings), trace C completes its repeating pattern most frequently across the screen. Its waveform, though complex in shape (indicating a rich musical timbre with harmonics), has the shortest period between repeating features. Trace D, by contrast, barely completes one gentle cycle across the entire screen width, giving it the lowest frequency and therefore the lowest pitch.

The amplitude (height) of the trace relates to loudness, not pitch. Traces can differ in both amplitude and frequency independently.