# AQA Definitions in Mechanics and Waves - AS Physics

Flashcards by Joven Alimambo, updated more than 1 year ago
 Created by Joven Alimambo over 5 years ago
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### Description

Definitions in mechanics and waves topic

## Resource summary

 Question Answer Scalars Scalars are quantities that have a magnitude Vectors Vectors are quantities that have a magnitude and direction Equilibrium For an object to be in equilibrium, there must not be any resultant force or moment acting on the object Elastic Collision In an elastic collision momentum and kinetic energy is conserved Inelastic Collision In an inelastic collision momentum is conserved but not kinetic energy Workdone A force can do work on an object or supply energy to it, if a force acts on the object whilst it moves Principle of Moments For an object to be in equilibrium, the sum of the clockwise moments is equal to the sum of the anticlockwise moments taken about any point Centre of Mass The centre of mass/ gravity of an object is the point through which the entire weight of the object is said to act Newton's 1st Law An object will remain at rest or move at a constant velocity in a straight line unless acted on by an external force Newton's 2nd Law When a body is acted on by an external force, it's acceleration is proportional to the force applied F=MA Newton's 3rd Law Everything has an equal and opposite reaction Terminal Velocity When an object falls to the ground or a car accelerates at it's maximum engine power the acceleration of the object will not remain constant Elastic Limit The greatest stress that can be applied to a material without causing permanent deformation Hooke's Law The extension is directly proportional to the force applied to it provided the elastic limit is not exceeded Tensile Stress Defined as the force per unit cross sectional area of a stretched wire Tensile Strain Defined as the extension per unit length for a stretched wire Young's Modulus Young's modulus of a material is the ratio of the tensile stress to tensile strain Mechanical Waves Produced by vibrations in a material medium (Eg. Sound waves, S and P waves) Electromagnetic waves They do not travel through a medium but can travel through a vacuum. They travel through space at the speed of light (Eg. Radio, Infrared, UV) Transverse Waves Oscillate at a right angle to the direction of the wave (Eg. EM waves) Longitudinal Wave Oscillate parallel to the direction of the wave (Eg. mechanical) When light enters an optically denser medium it refracts.. Towards the normal When light enters an optically less dense medium it refracts.. Away from the normal Conditions for TOTAL INTERNAL REFLECTION: *The angle of incidence must be greater than the critical angle *Light must travel from an optically dense medium to a less optically dense medium Cladding *prevents information to cross over from one fibre making it secure *Slightly lower refractive index compared to core making it totally internally reflect Optical Fibres (ADVANTAGE) *More information *More secure *Little energy lost (Copper loses energy through heat loss) Optical Fibres (DISADVANTAGE) *Impurity *Modal dispersion *Spectral dispersion Stationary Waves Produced when two waves of the same frequency, amplitude and constant phase difference travel in opposite directions through the same medium Coherent Sources Sources which have the same wavelength, frequency, and have a constant phase difference between them Monochromatic Light It's light of one wavelength or frequency Path difference The difference in distance travelled by one wave compared to the other Diffraction It's the spreading out of waves when they pass through an opening around an obstacle which is comparable in size to their wavelength

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