List_of_definitions

Prepared by: Lim Kang Hui ‘O’ Level Physics List of Definitions Term Definition 1 Measurement 1.1 Scalar A scalar quantity has a magnitude but no direction. 1.2 Vector A vector quantity has a magnitude and direction. 1.3 Precision Measure of how close a set of readings of the same physical quantity with each other 1.4 Accuracy Measure of how close a set of readings are to the true value. 2 Kinematics 2.1 Distance Length of path taken. 2.2 Displacement Net change in position of an object. 2.3 Freefall An object is in freefall when the only force acting on it is due to gravity. 2.4 Terminal Velocity A constant speed (with zero acceleration) at when the drag force of an object due to air resistance equals to the weight of the object such that it experiences zero net force. 3 Dynamics 3.1 Force A push or a pull on a body. 3.2 Newton’s first law of motion Every object will continue in its state of rest or uniform motion in a straight line unless a resultant force act on it. 3.3 Newton’s second law of motion When a resultant force acts on an object of a constant mass, the object will accelerate in the direction of the resultant force. The product of the mass m and acceleration anet of the object gives the resultant force. 3.4 Newton’s third law of motion If Body A exerts a force onto Body B, Body B will exert and equal and opposite force onto Body A. 3.5 Equilibrium Body is in equilibrium if the net force on the body is zero. (i.e., static system where no net acceleration takes place). 3.6 Normal force A component of the contact force that is perpendicular to the surface the object is in contact with. 3.7 Friction force A contact force that opposes or tends to oppose motion between surfaces in contact. 4 Mass, Weight, and Density 4.1 Mass Amount of matter in a body. 4.2 Inertia Reluctance of the object to change its state of rest or motion, due to its mass. 4.3 Weight Amount of force of gravity acting on an object. 4.4 Density Mass per unit volume 5 Turning Effect of Forces 5.1 Moment Product of a force F and the perpendicular distance from the pivot to the line of action of the force F. 5.2 Principle of moments When a body is in equilibrium, the sum of clockwise moments about a pivot is equal to the sum of anti-clockwise moments about the same pivot. 5.3 Centre of gravity Is a point where the weight of an object seems to be acting on, the centre of gravity can lie outside of an object. 5.4 Stability Measure of its ability to return to its original position after it is slightly displaced.

Prepared by: Lim Kang Hui 6 Pressure 6.1 Pressure Amount of force acting per unit area. 6.2 Atmospheric pressure Pressure at sea level (i.e., 1 atm = 101325 Pa = 760 mmHg = 76 cmHg) 7 Energy, Work, and Power 7.1 Energy Capacity to do work. 7.2 Principle of conservation of energy Energy cannot be created nor destroyed, but can be converted from one form to another. Total energy in an isolated system is a constant. 7.3 Kinetic energy Energy an object poss