Question 1
Most-appropriate topic codes (Cambridge IGCSE Physics 0625):
• Topic 1.4 — Density and volume (Parts (a), (b), (c))
▶️ Answer/Explanation
(a)
For the correct answer:
20 cm³
By observing the initial meniscus level in the measuring cylinder prior to adding the drops, the water aligns with the 20 mark. Thus, the initial volume is simply 20 cm³. In any laboratory setting, reading the bottom of the meniscus at eye level ensures accurate volume measurements.
(b)
For the correct answer:
0.25 cm³
To find the volume of a single drop, you first need to determine the total volume added. The volume increased from 20 cm³ to 25 cm³, meaning the 20 drops have a combined volume of 5 cm³. By dividing this total added volume (5 cm³) by the number of drops (20), we calculate the average volume of a single drop. This gives 5 / 20, which is exactly 0.25 cm³ per drop.
(c)
For the correct answer:
Use the displacement method.
First, pour a known volume of water into the measuring cylinder and record this initial volume. Next, carefully lower the irregularly shaped piece of metal into the water, ensuring it is completely submerged without splashing. Record the new, higher volume reading on the cylinder. The volume of the metal is simply the difference between the final volume and the initial volume, as the metal displaces a volume of water exactly equal to its own volume.
Question 2
Most-appropriate topic codes (Cambridge IGCSE Physics 0625):
• Topic 1.5.1 — Effects of forces (Part a)
• Topic 1.2 — Motion (Parts b, c)
▶️ Answer/Explanation
(a)
For the correct answer:
Size: 300 N
Direction: to the right / forwards
Since the forces are acting in opposite directions along the same horizontal plane, you subtract the smaller opposing force from the larger driving force. The forward force is 1200 N and the backward resistive force is 900 N. The resultant force is 1200 N – 900 N = 300 N. It acts in the direction of the larger force, which is to the right.
(b)(i)
For the correct answer:
7.20 s
Digital stop-watches usually display minutes, seconds, and hundredths of a second. The display reads “0:07 20”, which translates to 0 minutes, 7 seconds, and 20 hundredths of a second. Therefore, the total time elapsed is precisely 7.20 seconds.
(b)(ii)
For the correct answer:
15.6 m/s (or 15.625 m/s)
Average speed is calculated using the formula: Total Distance divided by Total Time. Here, the distance is given as 200 m, and the time taken for this specific stretch is 12.8 s. When we divide 200 by 12.8, we get 15.625. Rounding to three significant figures, the average speed is 15.6 m/s.
(c)
For the correct answer:
48 m
The distance travelled can be found by calculating the area under the speed-time graph between the given time intervals. Between t = 2.0 s and t = 6.0 s, the graph forms a trapezium. At 2.0 s, the speed is 6.0 m/s; at 6.0 s, the speed is 18.0 m/s. The area of the trapezium is 0.5 × (sum of parallel sides) × base = 0.5 × (6.0 + 18.0) × (6.0 – 2.0) = 0.5 × 24.0 × 4.0 = 48 metres. Alternatively, you can split the area into a rectangle and a triangle to get the same 48 m result.
Question 3
Most-appropriate topic codes (Cambridge IGCSE Physics 0625):
• Topic 1.5.2 — Turning effect of forces (Part a)
• Topic 1.7.1 — Energy (Parts b(i), b(ii))
▶️ Answer/Explanation
(a)
For the correct answer:
6000 N cm
The turning effect or moment of a force is calculated by multiplying the applied force by the perpendicular distance from the pivot. Here, the force is 200 N and the distance is 30 cm. Multiplying these together (200 × 30) gives a moment of 6000. Since the force is in Newtons and distance in centimetres, the unit is N cm.
(b)(i)
For the correct answer:
1. Chemical energy of the sailor to kinetic energy of the winch/sail.
2. Kinetic energy to gravitational potential energy of the sail.
When the sailor turns the winch, the chemical energy stored in their muscles is transferred into the kinetic energy of the rotating winch and the moving sail. As the sail is hoisted higher up the mast, this kinetic energy is further transferred into gravitational potential energy, which is a highly useful transfer for the specific task of raising the sail.
(b)(ii)
For the correct answer:
Kinetic energy to thermal (heat) energy due to friction.
In any mechanical system with moving parts, friction is inevitable. As the winch turns and ropes rub against pulleys, some of the input kinetic energy is dissipated as thermal energy (heat) and sound. This energy transfer is considered “non-useful” or wasted, as it does not contribute to raising the sail.
Question 4
Most-appropriate topic codes (Cambridge IGCSE Physics 0625):
• Topic 1.5.1 — Mass and weight (Part a)
• Topic 1.7.1 — Work and energy (Part b)
• Topic 1.8 — Pressure (Part c)
▶️ Answer/Explanation
(a)
For the correct answer:
50 N
Weight is the gravitational force acting on an object and is calculated using the equation W = mg, where m is mass and g is the acceleration due to free fall. With a mass of 5.0 kg and g taken as 10 m/s² (as per the exam instructions), the weight is 5.0 × 10 = 50 N. This shows the downward pull exerted by gravity on the mass.
(b)
For the correct answer:
75 J
According to the principle of conservation of energy, the work done in lifting an object vertically is directly transferred into its gravitational potential energy store, assuming no energy is lost to air resistance. Since the student did 75 J of work to lift the object, the object gains exactly 75 J of gravitational potential energy.
(c)
For the correct answer:
3.89 N/cm²
Pressure is defined as the force applied per unit area. First, calculate the total area of contact: the table has 4 legs, and each leg has an area of 18 cm², giving a total area of 4 × 18 = 72 cm². The total force exerted by the table is its weight, 280 N. Dividing the force by the total area (280 / 72) yields approximately 3.888… Rounding this to an appropriate precision gives 3.89, and the unit is N/cm².
Question 5
Use your ideas about molecules.
Most-appropriate topic codes (Cambridge IGCSE Physics 0625):
• Topic 1.8 — Pressure (Part a)
• Topic 2.1.3 — Pressure and volume at constant temperature (Part b)
▶️ Answer/Explanation
(a)(i)
For the correct answer:
876 mm of mercury
First, find the height difference ($h$) between the two columns of mercury, which represents the excess pressure of the gas over atmospheric pressure: 180 mm – 60 mm = 120 mm. Because the gas pushes the mercury level down lower on its side, the gas pressure is greater than atmospheric pressure. You calculate the total gas pressure by adding this difference to the atmospheric pressure: 756 mm + 120 mm = 876 mm of mercury.
(a)(ii)
For the correct answer:
Manometer
The device shown is a U-tube manometer. It is a standard scientific instrument used to measure the pressure difference between two fluids (in this case, the trapped gas and the open atmosphere) by observing the difference in fluid column heights.
(b)(i)
For the correct answer:
Gas molecules collide with the cylinder walls, exerting a force over an area.
According to the kinetic particle model, gases consist of freely moving molecules that travel at high speeds in random directions. When these molecules collide with the rigid inner walls of the cylinder, they experience a change in momentum, thus exerting a small outward force. The collective effect of millions of such molecular collisions across the internal surface area generates steady macroscopic gas pressure.
(b)(ii)
For the correct answer:
Pressure decreases because molecules hit the walls less frequently.
As the volume of the cylinder increases at a constant temperature (meaning the average speed of the molecules doesn’t change), the gas molecules spread out over a much larger space. Because they have more distance to cover between impacts, they collide with the walls of the cylinder less frequently. This reduction in the rate of collisions leads directly to a decrease in the overall pressure exerted on the cylinder walls.
Question 6
Most-appropriate topic codes (Cambridge IGCSE Physics 0625):
• Topic 3.1 — Wave properties (Parts a, b, c)
▶️ Answer/Explanation
(a)(i)
For the correct answer:
Refraction
The bending of wavefronts as they pass a boundary into a medium of different depth is called refraction. This phenomenon occurs universally with waves when they experience a sudden change in speed due to entering a different environment.
(a)(ii)
For the correct answer:
Property: Wavelength or Speed
Change: Decreases
When water waves transition from deep to shallow regions, their speed decreases due to increased interaction with the bottom. Because the frequency remains constant (dictated by the source), this drop in speed results in a proportional decrease in wavelength, meaning the wavefronts pack closer together.
(b)
For the correct answer:
2.5 Hz
Frequency represents the number of complete waves generated or passing a fixed point per second. If 25 waves are produced in 10 seconds, you divide the total number of waves by the time taken. 25 / 10 equals 2.5 waves per second, which is written as 2.5 Hertz (Hz).
(c)(i)
For the correct answer:
Any electromagnetic wave (e.g., light, radio waves, X-rays) or seismic S-waves.
Transverse waves are incredibly common in physics. Light waves, and indeed all members of the electromagnetic spectrum, travel as transverse waves. Another prominent example would be a wave generated by shaking a rope up and down.
(c)(ii)
For the correct answer:
Particles vibrate perpendicular (at right angles) to the direction of wave travel.
In a transverse wave, the physical oscillation of the medium’s particles is disjointed from the wave’s overall forward motion. While the wave energy propagates horizontally forward, the individual particles simply vibrate strictly up and down—at a $90^\circ$ angle—to that forward direction of energy transfer.
Question 7
Fig. 7.1 and Fig. 7.2 show the force between the magnet and the bar in each case.
Most-appropriate topic codes (Cambridge IGCSE Physics 0625):
• Topic 4.1 — Simple phenomena of magnetism (Parts a, b)
▶️ Answer/Explanation
(a)
For the correct answer:
The metal bar is a permanent magnet. End X is a South pole.
Only another permanent magnet can be repelled by a magnet; an unmagnetised magnetic material (like soft iron) would only experience attraction to both poles. Because end X repels the South pole of the test magnet, we can conclusively deduce that end X must itself be a South pole, following the rule that like poles repel.
(b)
For the correct answer:
Use iron filings or a plotting compass on the card.
To reveal the invisible magnetic field pattern, place the magnets securely under the card and sprinkle iron filings evenly across the top surface. Gently tap the card, which allows the filings to shift and align themselves along the magnetic field lines. Alternatively, you can systematically place a small plotting compass at various points around the magnets, drawing small pencil arrows indicating the needle’s direction to gradually map out the field lines from North to South.
Question 8
State the name of the particles flowing in the metal wire.
Calculate the potential difference (p.d.) across the 15 Ω resistor.
Most-appropriate topic codes (Cambridge IGCSE Physics 0625):
• Topic 4.3.1 — Circuit diagrams (Part a)
• Topic 4.2.1 — Electric charge and current (Part b)
• Topic 4.2.3 — Resistance (Part c)
▶️ Answer/Explanation
(a)
For the correct answer:
A series circuit showing the standard symbols for a battery, switch, ammeter, lamp, and resistor.
A proper schematic diagram uses universally recognised symbols instead of realistic sketches. You draw a single rectangular loop. In this loop, insert the battery symbol (long and short parallel lines), an open switch, an ‘A’ inside a circle for the ammeter, a circle with a cross for the lamp, and a blank rectangle for the 15 Ω resistor. All components must be connected in a continuous series loop without branching.
(b)
For the correct answer:
Electrons
In solid metallic conductors like copper wire, the positively charged atomic nuclei are fixed in a lattice structure. The only particles free to move and carry charge are the negatively charged delocalised electrons. When a potential difference is applied, it is these electrons that drift through the wire, creating the electric current.
(c)
For the correct answer:
6.0 V
You can find the potential difference across a component using Ohm’s Law, defined by the equation $V = IR$, where I is current and R is resistance. Multiplying the given current of 0.40 A by the resistor’s value of 15 Ω yields a potential difference of 6.0 Volts. This means 6 Joules of energy are used per Coulomb of charge passing through the resistor.
Question 9
Most-appropriate topic codes (Cambridge IGCSE Physics 0625):
• Topic 4.4 — Electrical safety (Parts a(i), a(ii))
• Topic 4.5.6 — Transformers (Parts b, c)
▶️ Answer/Explanation
(a)(i)
For the correct answer:
To protect the circuit/appliance from overheating or catching fire due to excessive current.
A fuse acts as a crucial safety device in electrical systems. By breaking the circuit during a surge, it prevents dangerous amounts of current from flowing into the transformer, thereby preventing wires from overheating and reducing the risk of an electrical fire.
(a)(ii)
For the correct answer:
It contains a thin wire that melts when the current is too high, breaking the circuit.
A fuse is designed with a very thin piece of resistive wire inside. As current flows through it, the wire heats up. If a fault causes the current to exceed the fuse’s specific rating, the heat becomes so intense that the wire physically melts and snaps. This permanently breaks the conductive path, instantly stopping the flow of dangerous electricity.
(b)
For the correct answer:
110 V (or 109.87 V)
The relationship between voltages and coil turns in a transformer is governed by the transformer equation: $\frac{V_p}{V_s} = \frac{N_p}{N_s}$. Plugging in the values, we get $\frac{230}{V_s} = \frac{314}{150}$. Rearranging to solve for the secondary voltage gives $V_s = \frac{230 \times 150}{314}$. The result is approximately 109.87 V, which rounds to 110 V for standard practical applications.
(c)(i)
For the correct answer:
Soft iron
Transformers rely on efficiently linking magnetic fields between two coils. Soft iron is the ideal core material because it is easily magnetised and demagnetised (it is magnetically ‘soft’) by the alternating current, allowing for minimal energy loss during the continuous magnetic reversals.
(c)(ii)
For the correct answer:
Copper
The coils need to carry alternating current with as little electrical resistance as possible to prevent energy waste in the form of heat. Copper is an excellent electrical conductor and is relatively malleable, making it the perfect choice for winding transformer coils.
(c)(iii)
For the correct answer:
It has fewer turns on the secondary coil than on the primary coil.
A step-down transformer serves to decrease the output voltage relative to the input voltage. Visually and mathematically, this is achieved by winding significantly fewer turns of wire on the secondary side (150 turns) compared to the primary input side (314 turns). The voltage reduction is directly proportional to this drop in coil turns.
Question 10
Most-appropriate topic codes (Cambridge IGCSE Physics 0625):
• Topic 5.2.2 — The three kinds of nuclear emission (Part a)
• Topic 5.1.1 — Atomic model (Part b)
• Topic 5.2.4 — Half-life (Part c)
▶️ Answer/Explanation
(a)
For the correct answer:
Gamma rays are high-frequency electromagnetic waves, which makes them highly penetrating but the least likely to physically interact and ionise atoms. Alpha particles are heavy, slow, and highly charged (like a helium nucleus consisting of 2 protons and 2 neutrons), meaning they ionise strongly but are easily stopped, making them the least penetrating. Beta particles are high-speed, fast-moving electrons, which gives them a distinct negative charge.
(b)
For the correct answer:
$^{241}_{94}\text{Pu}$
Nuclide notation requires the mass number (nucleon number) at the top left and the atomic number (proton number) at the bottom left of the chemical symbol. The atomic number is given as 94. The total mass number is the sum of protons and neutrons, which is 94 + 147 = 241. Placing these around the symbol Pu gives the complete notation.
(c)
For the correct answer:
$2.0\times 10^{12}$ atoms
A half-life is the time it takes for exactly half of the unstable nuclei in a sample to decay. Since the half-life is 14 years, a total duration of 28 years represents exactly two half-lives (28 / 14 = 2). After the first half-life, the number halves to $4.0\times 10^{12}$. After the second half-life, it halves again, leaving $2.0\times 10^{12}$ undecayed plutonium atoms.