OCR A A-Level Physics Definitions Paper 1 Summary and Study Guide

▪ What are the SI base units? - Ans Metre, kilogram, ampere, mole, second, kelvin ▪ Scalar quantity - Ans Has magnitude but no direction ▪ Vector quantity - Ans Has both magnitude and direction ▪ Acceleration - Ans rate of change of velocity ▪ Define the Newton - Ans the force that causes a mass of 1kg to have an acceleration of 1ms^-2 in the direction of the force ▪ Tension - Ans The force within a stretched cable or rope ▪ Normal contact force - Ans The force that arises when one object rests against another ▪ Upthrust - Ans An upward buoyancy force acting on an object when it is in a fluid ▪ Friction - Ans A force that opposes motion between two surfaces that are in contact ▪ Drag - Ans The frictional force experienced by an object travelling through a fluid ▪ moment - AnsForce x perpendicular distance from point of rotation ▪ Principle of moments - AnsFor a body in rotational equilibrium, the sum of the anticlockwise moments about a point is equal to the sum of the clockwise moments about the same point ▪ Centre of gravity - AnsThe point where the entire weight of an object appears to act. ▪ Centre of mass - AnsA point through which any externally applied force produces straightline motion but no rotation ▪ Torque - Ansone of the forces x perpendicular separation between the forces ▪ Density - AnsMass per unit volume ▪ Pressure - AnsForce per unit area. ▪ Pressure in a fluid at any depth... - Anssame in all directions ▪ Archimede's Principle - AnsThe upthrust exerted n a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces ▪ Joule - Ans1 Nm ▪ Energy - Ansthe capacity to do work ▪ Principle of conservation of energy - AnsThe total energy of a closed system remains constant; energy can not be created or destroyed, only transferred from one form to another ▪ Power - Ansthe rate at which work is done ▪ Watt - AnsOne joule per second ▪ Hooke's Law - AnsThe extension of a spring is directly proportional to the force applied, as long as the elastic limit is not exceeded ▪ Tensile stress - AnsForce per unit cross-sectional area ▪ Tensile strain - AnsThe fractional change in the original length of the wire ▪ Ultimate tensile strength - AnsThe maximum stress that a material can withstand before it breaks ▪ Young Modulus - AnsThe ratio of stress to strain for a particular mate