SCIENCE (PHYSICS) – Paper 2 Physics (set 2.9) – mark scheme

“A physical quantity is a quantity that can be measured. It consists of a numerical magnitude and a unit.”

“Scalar quantities are physical quantities that have only magnitude.”

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

“The total length covered by a moving object regardless of the direction of motion”

“The distance measured in a straight line in a specified direction”

“Speed is the distance travelled per unit time. Its SI unit is metre per second (m/s).”

“Velocity is the rate of change in displacement. Its SI unit is metre per second (m/s).”

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

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

“The gradient of a speed-time graph of an object gives the acceleration of the object.”

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

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

“Pressure is the force acting per unit area.”

“The pressure is maximum when the contact area is minimum.”

“Newton's First Law of Motion states that every object will continue in its state of rest or uniform motion in a straight line unless a resultant force acts on it.”

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

“Action and reaction forces act on different bodies.”

“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.”

“Thus, using a longer spoon creates a greater turning effect.”

“The moment of a force M, or torque about a pivot is the product of the force F and the perpendicular distance d from the pivot to the line of action of the force.”

“During condensation and solidification, energy is transferred out of the substance. The average separation of the particles decreases and so the potential energy of the particles decreases.”

“However, during these processes of changing states, the average kinetic energy of the particles remains constant. Hence, the temperature stays constant.”

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

“The liquid at the bottom of the pot expands due to heating via conduction through the bottom of the pot.”

“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.”

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

“A transverse wave has a direction of vibration that is perpendicular to the direction of wave travel (Figure 9.9).”

“A longitudinal wave has a direction of vibration that is parallel to the direction of wave travel (Figure 9.10).”

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

“Sound travels when the vibrations of atoms are passed on to neighbouring atoms.”

“Infrared thermometers detect the characteristics of the infrared emitted by a person to determine the body temperature. The same technology can detect and construct the temperature map of a subject of object.”

“X-rays are used to scan manufactured goods for hidden defects and cracks.”

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

“A device made of glass or other transparent material that is able to concentrate light rays is called a converging lens (Figure 12.33).”

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

“In this arrangement, the lens will function as a magnifying glass. Hence the viewer will see an enlarged image of the object.”

“A virtual image cannot be formed on a screen placed at its image plane.”

“In a series circuit, the current at every point is the same.”

“In a series circuit, the current at every point is the same.”

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

“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.”

“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.”

“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.”

“When two pieces of magnets are placed together, the like poles of the magnet repel while the unlike poles attract (Figure 16.2).”

“We can determine if an object is a magnet or not by whether it gets repelled by another magnet (Figure 16.7).”

“The magnetic field lines never cross one another.”

“By convention, the field lines have arrows that point out from the north pole of the magnet and point into the south pole.”

“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.”

“An atom consists of a positively charged nucleus (plural: nuclei) and negatively charged electrons moving around the nucleus (Figure 17.1).”

“The nucleus of an atom consists of two types of particles — protons and neutrons.”

“In a neutral atom, the total positive charge equals the total negative charge. Therefore, in a neutral atom, the number of protons is the same as the number of electrons.”

“A detector measures the amount of radiation passing through. If the material is too thick, the amount of radiation is low and vice versa.”

“The energy carried by the radiation can kill cells, and cause mutation and cancer.”

“Like charges repel each other while unlike charges attract each other.”

“Like charges repel each other while unlike charges attract each other.”

“Like charges repel each other while unlike charges attract each other.”

“The longer the cylinder, the more collisions the electrons will make with its atom. Hence, the resistance R of the cylindrical resistor is directly proportional to the length of the cylinder l.”

“The larger the cross-sectional area A of the cylinder, the greater the number of electrons that can flow through it. Therefore, the resistance R of the cylindrical resistor is inversely proportional to the area of the cylinder A.”

“A fuse has to have a current rating greater than the current drawn. Otherwise the fuse will blow even before the kettle can work.”

“A fuse is a safety device added to an electric circuit to prevent excessive current flow. It consists of a strip of fusible wire that will melt when the current flowing through it exceeds a certain value (Figure 15.12(a)).”

“One kW h of electricity is the energy used by a 1 kW device in an hour.”

“First, the left hand is held out with the forefinger, second finger and thumb perpendicular to each other (Figure 16.53). Next, the first finger is oriented in the direction of the magnetic field from north to south, and the second finger in the direction of conventional current. The resultant force that is induced by the current-carrying conductor will be given by the direction the thumb is pointing to.”

“Fleming's left-hand rule is used to find either the direction of the force, magnetic field or current when the directions of any two of these are known.”

“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.”

“The current-carrying coil experiences an equal force on parts AB and CD of the coil. This force is created by the motor effect on each side of the coil.”

“The forces produce a turning effect that is equal in magnitude on each wire.”