--- title: "Leaving Cert Physics — Example Quiz" tags: [physics, leaving-cert, science, second-level] time_limit: 30 allow_overrun: true random_order: false --- ##### Question q001 type: single_choice correct: [c] A car accelerates uniformly from rest to 20 m s⁻¹ in 8 seconds. What is its acceleration? A. 160 m s⁻² B. 0.4 m s⁻² C. 2.5 m s⁻² D. 28 m s⁻² ###### Explanation Acceleration is the change in velocity divided by time: (20 − 0) ÷ 8 = 2.5 m s⁻². Multiplying rather than dividing gives the distractor 160, which is why the units are worth checking — m s⁻¹ divided by s gives m s⁻². --- ##### Question q002 type: single_choice correct: [b] Which of the following is a **vector** quantity? A. Speed B. Velocity C. Mass D. Energy ###### Explanation A vector has both magnitude and direction. Velocity is speed in a stated direction, so it is a vector; speed alone is scalar. Mass and energy are scalars. This distinction matters because two objects can have equal speed and opposite velocity. --- ##### Question q003 type: true_false correct: [b] The weight of an object is the same on the Moon as on Earth. ###### Explanation False. Weight is the force of gravity on a mass, W = mg. The Moon's gravitational field strength is about one sixth of Earth's, so weight is about one sixth. **Mass** is what stays the same — it is a measure of the amount of matter. --- ##### Question q004 type: single_choice correct: [d] A resistor of 4 Ω carries a current of 3 A. What is the potential difference across it? A. 0.75 V B. 1.33 V C. 7 V D. 12 V ###### Explanation From Ohm's law, V = IR = 3 × 4 = 12 V. Dividing instead of multiplying produces the two smaller distractors, and adding produces 7. --- ##### Question q005 type: multi_choice correct: [a, c] Which TWO of the following are **transverse** waves? (Select two.) A. Light B. Sound in air C. Water surface waves D. Ultrasound in air ###### Explanation In a transverse wave the oscillation is perpendicular to the direction of travel — true of light and of water surface waves. Sound in air, including ultrasound, is longitudinal: the air oscillates along the direction of travel as compressions and rarefactions. --- ##### Question q006 type: single_choice correct: [b] A wave has a frequency of 50 Hz and a wavelength of 4 m. What is its speed? A. 12.5 m s⁻¹ B. 200 m s⁻¹ C. 54 m s⁻¹ D. 0.08 m s⁻¹ ###### Explanation The wave equation gives c = fλ = 50 × 4 = 200 m s⁻¹. Dividing frequency by wavelength gives 12.5, a common slip when the equation is recalled the wrong way round. --- ##### Question q007 type: single_choice correct: [c] Which colour of visible light has the **longest** wavelength? A. Blue B. Green C. Red D. Violet ###### Explanation Red is at the long-wavelength, low-frequency end of the visible spectrum; violet is at the short-wavelength, high-frequency end. Because c = fλ is fixed for light in a vacuum, the longest wavelength necessarily has the lowest frequency. --- ##### Question q008 type: sequence correct: [d, b, a, c] Arrange the following parts of the electromagnetic spectrum in order of **increasing frequency**. A. Visible light B. Infrared C. X-rays D. Radio waves ###### Explanation The order by increasing frequency is radio, microwave, infrared, visible, ultraviolet, X-ray, gamma. Increasing frequency means decreasing wavelength and increasing photon energy, which is why X-rays are ionising and radio waves are not. --- ##### Question q009 type: single_choice correct: [a] What is the SI unit of **power**? A. Watt B. Joule C. Newton D. Pascal ###### Explanation Power is the rate of doing work, measured in watts, where one watt is one joule per second. The joule is the unit of energy, the newton of force, and the pascal of pressure. --- ##### Question q010 type: true_false correct: [a] In a series circuit, the current is the same at every point. ###### Explanation True. A series circuit provides only one path, so charge cannot accumulate anywhere and the current is identical throughout. It is the potential difference that divides between the components, summing to the supply voltage. --- ##### Question q011 type: single_choice correct: [c] Which type of radiation is **most** penetrating? A. Alpha B. Beta C. Gamma D. All are equally penetrating ###### Explanation Gamma radiation is high-energy electromagnetic radiation, stopped only by thick lead or concrete. Beta particles are stopped by a few millimetres of aluminium, and alpha particles by paper or a few centimetres of air. The order of penetration is the reverse of the order of ionising power. --- ##### Question q012 type: single_choice correct: [b] An object of mass 2 kg is raised 5 m. Taking g as 10 m s⁻², what is the gain in gravitational potential energy? A. 10 J B. 100 J C. 25 J D. 1000 J ###### Explanation Potential energy gained is mgh = 2 × 10 × 5 = 100 J. Omitting g gives 10 J, and it is worth noting that this is the *gain* in potential energy — the total depends on where the zero is taken. --- ##### Question q013 type: multi_choice correct: [b, d] Which TWO statements about **refraction** are correct? (Select two.) A. The frequency of the light changes as it enters the new medium B. The speed of the light changes as it enters the new medium C. Refraction occurs only when light enters at 90° to the surface D. The wavelength of the light changes as it enters the new medium ###### Explanation Refraction is caused by a change in the speed of light between media, and since frequency is set by the source and does not change, the wavelength must change instead. Light entering along the normal (at 90° to the surface) slows down but does **not** change direction. --- ##### Question q014 type: single_choice correct: [b] What does a **thermistor** do as its temperature rises? A. Its resistance increases B. Its resistance decreases C. Its resistance stays constant D. It stops conducting entirely ###### Explanation In the negative temperature coefficient thermistors used at this level, resistance falls sharply as temperature rises, because more charge carriers are released. This behaviour is the opposite of a metallic conductor, whose resistance increases with temperature. --- ##### Question q015 type: single_choice correct: [d] Newton's third law states that: A. Force equals mass times acceleration B. An object stays at rest unless acted on by a force C. Momentum is conserved in all collisions D. For every action there is an equal and opposite reaction ###### Explanation The third law concerns paired forces acting on **different** bodies. A is the second law, B is the first. The key point often missed is that the action and reaction act on different objects, which is why they do not cancel out. --- ##### Question q016 type: single_choice correct: [c] Which quantity is measured in **coulombs**? A. Current B. Potential difference C. Charge D. Resistance ###### Explanation The coulomb is the unit of electric charge. Current is measured in amperes, where one ampere is one coulomb per second; potential difference in volts; resistance in ohms. --- ##### Question q017 type: true_false correct: [b] Sound waves can travel through a vacuum. ###### Explanation False. Sound is a mechanical wave and requires a medium whose particles can be compressed and rarefied. A vacuum has no such particles, which is why a ringing bell inside an evacuated jar becomes inaudible while remaining visible — light needs no medium. --- ##### Question q018 type: single_choice correct: [b] A machine does 600 J of work in 30 seconds. What is its power output? A. 0.05 W B. 20 W C. 630 W D. 18000 W ###### Explanation Power is work divided by time: 600 ÷ 30 = 20 W. Multiplying gives 18000, and inverting the fraction gives 0.05. --- ##### Question q019 type: single_choice correct: [a] The **specific heat capacity** of a substance is the energy needed to: A. Raise the temperature of 1 kg of it by 1 K B. Melt 1 kg of it at its melting point C. Vaporise 1 kg of it at its boiling point D. Raise the temperature of any mass of it by 1 K ###### Explanation Specific heat capacity is per kilogram, per kelvin. Options B and C describe the specific latent heats of fusion and vaporisation, which occur at constant temperature. Option D omits the fixed mass, which is what makes the quantity "specific". --- ##### Question q020 type: single_choice correct: [c] In the photoelectric effect, electrons are emitted from a metal surface only when the incident light is above a certain: A. Intensity B. Wavelength C. Frequency D. Angle of incidence ###### Explanation There is a threshold **frequency** below which no electrons are emitted regardless of how intense the light is. This was the observation that classical wave theory could not explain and that Einstein accounted for with photons, each carrying energy E = hf. ---