AQA Physics Unit 3 (P3) Mindmap

Mindmap to highlight key points in the Unit 3 Physics specification

• Created by: Triciaaa
• Created on: 15-04-13 14:37
• Physics Unit 3
• Using Physics to Make Things Work
• Moments
• Turning effect of a force
• m=fd
• clockwise =anticlockwise
• Levers = force magnifiers
• Stability - line of action lies outside base >resultant moment > topple
• Circular Motion
• Centripetal force=tension, gravity, friction
• Depends on mass, speed, radius
• constant change in direction causing object to accelerate towards centre
• Centre of Mass
• point where its mass is thought to be concentrated
• Freely suspended, rest at COM, directly below point of suspension
• Symmetrical Asymmetrical shapes
• Pendulum t=1/f
• Hydraulics
• incompressible, pressure transmitted equally in all directions
• car braking systems,car jacks
• P= F/cross sectional area
• Keeping Things Moving
• The Motor Effect
• Magnetic field: regions where magnetic materials and wire carrying currents experience a force
• Electromagnets magnify and demagnify
• cranes - iron steel works
• experiencing full force = wire must be 90º to MF
• Flemings Left Hand
• Thumb: Motion
• First finger: field
• Second finger: current
• Transformers
• Step up: more turns on 2nary
• only works on AC
• Step down: more turns on 1st
• changing current produces changing MF, inducing the secondary coil
• current of 1st inc/dec steadily, constant voltage induced in 2nd
• Medical Applications of Physics
• X-Rays
• High frequency, short wavelength, ionising
• Absorbed  by metal and bone, transmitted by healthy tissue
• CT scans, treating cancer
• Ultrasound
• High frequency (<20,000Hz)
• Non ionising, longitudinal waves
• when the wave hits a boundary, some is transmitted and reflected
• Ultrasound imaging = time taken for reflection  to reach detector
• S=V x T
• breaking down kidney stones, prenatal scanning
• Lenses
• Refractive index n = sin(i)/sin(r)
• Convex (converges rays together)
• Magnifies  (depends on distance away from object)
• Concave (diverges rays away)
• Always = virtual, upright, diminished
• Virtual and real rays
• Eye
• Retina, lens, cornea, pupil, iris, ciliary muscle, suspensory ligaments
• Far point = infinity
• Near point = 25cm
• Short sight - eyeball too long, cornea and lens too powerful
• Long sight - eyeball too short, cornea and lens too weak
• Other uses
• Optical fibres - endoscopes
• Lasers - cauterise
• Refractive index = 1/sin(c)
• Angle of incidence> critical angle = TIR
• current of 1st inc/dec steadily, constant voltage induced in 2nd