SCIENCE (PHYSICS) – Paper 2 Physics (set 2.3) – mark scheme

“Vector quantities are physical quantities that have both magnitude and direction.”

“Its displacement is zero, because it returns to A.”

“This type of force between objects that are in contact is known as contact force.”

“Non-contact forces are those that do not require objects to be in contact to exist.”

“A gravitational field is a region in which a mass experiences a force due to gravitational attraction.”

“Gravitational field strength g is defined as the gravitational force per unit mass placed at that point.”

“Mass is a measure of the amount of matter in a body.”

“On the other hand, the same 1 kg mass on the moon experiences a gravitational force of only 1.6 N. This is because the gravitational field strength on the moon is 1.6 N/kg.”

“The elephant would weigh much more on Earth’s surface than on the moon’s surface even though its mass remains unchanged.”

“Friction opposes motion between surfaces in contact.”

“Friction enables the tyres to grip the road surface and roll without slipping.”

“The principle of moments states that when a body is in equilibrium, the sum of clockwise moments about a pivot is equal to the sum of anticlockwise moments about the same pivot.”

“The principle of conservation of energy states that energy cannot be created or destroyed. Energy can be transferred from one store to another. The total energy of an isolated system is constant.”

“Power is defined as the work done or energy transferred per unit time.”

“Solids have a fixed volume and a fixed shape.”

“Liquids have a fixed volume and no fixed shape.”

“Gases have no fixed volume (compressible) and no fixed shape. A gas takes up the volume and shape of its container.”

“Gases have the lowest densities.”

“Particles are slightly less closely packed than in solids and arranged in an irregular pattern.”

“The particles slide over each other throughout the liquid without fixed positions.”

“Particles are very far apart from one another in an irregular pattern.”

“The particles can move freely in any direction.”

“However, metals consist of tiny particles called free electrons that are absent in most non-metals.”

“Due to their small size and high speed, the free electrons move very fast through the metal and transfer energy easily.”

“The warm liquid, being less dense than its surroundings, will rise. The cold liquid, being denser, will sink.”

“At the same time, the surrounding denser liquid sinks to take the place of the rising liquid.”

“Radiation is the process of energy transfer by electromagnetic waves. It does not require a medium.”

“The shiny, smooth and light-coloured surface of an object absorbs incoming radiation at a slower rate. The same surface also emits radiation at a slow rate. Hence, a poor emitter of radiation is also a poor absorber of radiation. The reverse is true for matt, rough and dark-coloured surfaces.”

“Sound is a longitudinal wave created by a vibrating source.”

“This is because there is no medium to transmit sound waves. Sound travels when the vibrations of atoms are passed on to neighbouring atoms.”

“A wave is a disturbance that propagates through space, transferring energy with it but not matter.”

“In the electromagnetic spectrum, electromagnetic waves are arranged in order of their frequency or wavelength.”

“The high-energy ionising radiations can knock electrons out from atoms and molecules to create harmful ions.”

“As higher frequency electromagnetic waves can penetrate deeper into the body to create ions, they are more harmful than radiations which do not penetrate as deeply.”

“The perpendicular line (90 °) to the surface at the point of incidence is called the normal.”

“The second law of reflection states that the angle of incidence θi is equal to the angle of reflection θr.”

“The angle between the incident ray and the normal is called the angle of incidence (θi).”

“The angle of refraction is the angle between the refracted ray and the normal at the point of incidence.”

“The refractive index n of a medium is defined as the ratio of the speed of light in a vacuum to the speed of light in the medium.”

“Electron flow is opposite in direction to conventional current.”

“The flow of electrons from the negative terminal of the battery to the positive terminal is opposite to the conventional current.”

“The resistance R of a component is the ratio of the potential difference V across it to the current I flowing through it.”

“In a parallel circuit, the total current flowing into or out of the parallel branches is equal to the sum of the individual currents in each parallel branch.”

“In a parallel circuit, the p.d. across the parallel branches is the same.”

“Induction, or induced magnetism, can take place when a magnetic material is placed close to a strong magnet or within a current-carrying solenoid.”

“Like magnetic poles repel and unlike magnetic poles attract.”

“Conversely, when two like poles are placed next to each other, the field lines move away from each other (Figure 16.33).”

“The direction of the magnetic field is given by the arrow.”

“The direction of the emissions and the time between emissions cannot be predicted.”

“In other words, it is not possible: to make the radioactive nucleus emit radiation by heating, cooling, chemical means or any other method;”

“Nuclear decay is a random process by which an unstable atomic nucleus loses its energy by emission of electromagnetic radiation or particle(s).”

“An α-particle consists of two protons and two neutrons tightly bound together.”

“A proton is positively charged.”

“A neutron does not carry any charge.”

“The live wire is usually brown.”

“The neutral wire is blue and is kept at zero voltage.”

“Switches and safety features such as fuses and circuit breakers have to be connected to the live wire in order to break or complete a circuit.”

“Consider the case in Figure 15.19 where the switch is connected to the neutral wire instead. Then the appliance becomes “live” and can create an electric shock when a person touches it even when the switch is open.”

“An earthed metal casing is a metal housing that encloses the electrical parts of an appliance and is connected to the earth, keeping the user safe in the event of an electrical fault. The live current passing through the earth metal casing flows to the ground. As Earth wire has very little resistance, it is likely that the fuse will be blown. This prevents further current flow.”

“Double insulation, as the name suggests, has two layers of insulation to enclose all exposed metalwork and “live” parts.”

“The graph has zero gradient.”

“The graph has an increasing gradient. The speed of the car increases.”

“The graph has a constant gradient.”

“The gradient of a distance–time graph of an object gives the speed of the object.”

“Acceleration due to gravity g is a constant. For objects close to Earth’s surface, the value of g is generally taken to be 9.8 m/s². For simplicity in calculations, we take this value to be 10 m/s² throughout this book, unless otherwise stated.”

“Acceleration due to gravity g is a constant.”

“Energy is transferred from a region of higher temperature (hotter object) to a region of lower temperature (cooler object) until both regions have the same temperature.”

“The two regions are said to be in a state of thermal equilibrium.”

“In general, metals are better thermal conductors than non-metals.”

“The warm liquid, being less dense than its surroundings, will rise. The cold liquid, being denser, will sink.”

“A larger surface area will emit energy at a higher rate via radiation.”

“Attraction can also take place between a magnet and an object that is made of an unmagnetised magnetic material. However, repulsion can only occur between two magnets.”

“The bar is a magnet if and only if it is repelled by one of the poles of the magnet.”

“When iron filings are sprinkled onto a bar magnet, most of the iron filings are attracted to the two ends of the magnet”

“This effect can be demonstrated using the set-up in Figure 16.50.”

“When the switch is closed, the copper wire frame immediately swings outwards (Figure 16.51(a)).”

“If the connection of the terminals is reversed, the copper wire frame swings in the opposite direction. The copper wire frame will also swing in the opposite direction if the polarity of the magnet is reversed.”

“Reversing the direction of current induces a swing in the opposite direction.”

“Reversing the polarity of the magnet also reverses the direction of the swing.”