SCIENCE (PHYSICS) – Paper 2 Physics (set 2.7) – mark scheme

“Table 1.3 shows the measuring range, smallest division as well as the common usage of the measuring instruments.”

“The smallest unit an instrument can measure is known as its precision.”

“An object undergoes non-uniform acceleration if the change in its velocity for every unit of time is not the same (Table 2.4).”

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

“Mass of a body depends on the number and composition of atoms and molecules.”

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

“Forces on an object at rest or moving at a constant velocity are balanced.”

“Thus, for every action, there is an equal and opposite reaction.”

“The turning effect of the force is proportional to: the perpendicular distance from the pivot where the force is applied; and the magnitude of the force applied.”

“That is why it is easier to lift the lid with a longer spoon.”

“The centre of gravity for an object that has a regular shape and uniform density is at the centroid or centre of the object.”

“A stretched rubber band or a compressed spring has energy in the elastic potential store (elastic potential energy).”

“mechanically (by a force acting over a distance);”

“Temperature rises with the average kinetic energy of the particles in a body and vice versa.”

“Internal energy is an energy store that is made up of the total kinetic energy associated with the random motion of the particles and the total potential energy between the particles in the system.”

“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. This difference in density results in convection currents (Figure 8.9).”

“All electromagnetic waves can travel without a medium and they all travel at the same speed of 3 × 10⁸ m/s in a vacuum.”

“A mobile phone converts sound waves to microwave signals.”

“Infrared thermometers detect the characteristics of the infrared emitted by a person to determine the body temperature.”

“At airports, X-rays are used to scan luggages for hazardous materials.”

“When you tune in to a radio station, sound is encoded and transmitted through the air to your radio set via radio waves (Figure 11.5).”

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

“The angle between the reflected ray and the normal is called the angle of reflection”

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

“The point on the principal axis where all rays parallel to the principal axis meet after passing through the lens”

“An electron is negatively charged while a proton is positively charged. The SI unit of electric charge is the coulomb (C).”

“Overheated circuits can cause fire and even explosions.”

“Too many plugs connected to a socket”

“Exposed wires are hazardous as they can cause electric shocks when touched accidentally.”

“The live wire is usually brown. It carries both the high voltage and the current.”

“The neutral wire is blue and is kept at zero voltage. It completes the path for current to flow through appliances in the electrical circuit.”

“The earth wire is yellow and green. It is a safety wire that is needed to earth appliances with a metal case.”

“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.”

“The switch disconnects the live wire from the metal casing”

“Proximity induced magnetism can take place when a magnetic material is in close proximity or in contact with a strong magnet (Figures 16.10 and 16.11).”

“When two unlike poles are placed next to each other, field lines go from the north pole of one magnet to the south pole of the other magnet (Figure 16.32).”

“If we grip the conductor with our thumb pointing in the direction of the conventional current, the curl of the fingers shows the direction of the magnetic field (Figure 16.41).”

“The strength of magnetic field increases when the current is increased (Figure 16.42).”

“Number of neutrons = nucleon number A - proton number Z in a nucleus”

“Isotopes are atoms of the same element that have the same numbers of protons but different numbers of neutrons.”

“Background radiation refers to nuclear radiation in an environment where no radioactive source has been deliberately introduced.”

“Natural background radiation accounts for about 80% of the radiation that we are exposed to.”

“Electric current is the rate of flow of charge and not charged particles.”

“The SI unit for current is ampere (A) or coulomb (C) per second (s).”

“The electromotive force (e.m.f) of an electrical source is the work done by the source in driving a unit charge around a complete circuit.”

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

“The imaginary line that joins all adjacent points on the wave that are moving in step is called a wavefront.”

“In Section 4.1, we have been using arrows to represent forces acting on individual objects. These diagrams are called free-body diagrams.”

“Friction is the contact force that opposes or tends to oppose motion between surfaces in contact.”

“The friction between the tyres and the slope prevents the vehicle from sliding down.”

“The principle of conservation of energy states that energy cannot be created or destroyed. Energy can be transferred from one store to another.”