and I know the recent how to basics are horrible, so here is a how to basic physics to make up for the crappy ones.
PHYSICS. 3SF EVERYTHING. REMEMBER.
Physical Quantities √
Kinematics √
Dynamics √
Mass, Weight and Density √
Turning Effect of Forces √
Work, Energy and Power √
Pressure √
Kinetic Theory of Matter √
Light √
Waves √
Electromagnetic Spectrum √
Sound √
Temperature √
1m/s = 3.6km/h
1g/cm^3 = 1000kg/m^3
Physical quantity: a quantity that can be measured, consists of a numerical magnitude and a unit.
Prefixes: nano(n) 10^-9, micro(µ) 10^-6, milli(m) 10^-3, centi(c) 10^-2, deci(d) 10^-1, kilo(k) 10^3, mega(M) 10^6, giga(G) 10^9.
Ruler: eye placed vertically above mark to avoid parallax error, middle of the ruler used to avoid zero error (worn-out ends).
Vernier calliper: zero error = positive (>0) or negative (<0), reading = main scale (1mm) + vernier scale (0.1mm), corrected reading = reading - zero error.
Micrometer screw gauge: tighten using ratchet, zero error = positive (>0) or negative (<0), reading = main scale (0.5mm) + thimble scale (0.01mm), corrected reading = reading - zero error.
Pendulum: oscillation = 1 complete to-and-fro motion, period = time taken for 1 complete oscillation. f = 1/T, f is frequency (Hz), T is period (s).
Stopwatch: 0.01s, human reaction time.
Scalar: magnitude only (distance, speed, mass, energy, time).
Vector: magnitude and direction (displacement, velocity, acceleration, force).
Distance: total length covered by an object, irrespective of direction of motion.
Speed: distance moved per unit time. v = d/t, v is speed (m/s), d is distance (m), t is time taken (s). average = total distance/total time = (initial speed + final speed)/2 if uniform acceleration.
Displacement: straight-line distance moved in a specified direction from reference (initial) point.
Displacement-time graph: gradient = velocity.
Velocity: rate of change of displacement. v = d/t, v is velocity (m/s), d is displacement (m), t is time taken (s).
Velocity-time graph: gradient = acceleration, area under graph = distance/displacement.
Acceleration: rate of change in velocity, uniform acceleration = constant rate of change in velocity. a = (v-u)/t, a is acceleration (m/s^2), v is final velocity (m/s), u is initial velocity (m/s), t is time taken (s).
Free-fall through air: acceleration = 10m/s^2, decreases to terminal (constant) velocity (0m/s^2), which is achieved when weight = air resistance.
Newton's 1st Law: every object will continue in its state of rest or uniform motion in a straight line unless a resultant force acts on it.
Newton's 2nd Law: when a resultant force acts on an object of a constant mass, the object will accelerate in the direction of the resultant force. F = ma, F is resultant force (N), m is mass (kg), a is acceleration (m/s^2)
Newton's 3rd Law: if body A exerts a force on body B, body B will exert an equal and opposite force on body A.
Friction: contact force that opposes/tends to oppose motion between surfaces in contact.
Effects of forces on motion: moves a stationary object, stops a moving object, changes the speed of a moving object, changes the direction of a moving object.
Vector diagram: 2 vectors pointing in the same direction, |magnitude| of A + |magnitude| of B = resultant force. 2 vectors pointing in opposite directions, |magnitude| of A - |magnitude| of B = resultant force, 2 vectors pointing in other directions, scale diagram.
Free body diagram: forces of different nature acting on 1 body (weight, normal force, friction, push/pull), uniform acceleration/stationary = equal magnitude.
Action-reaction pair: forces of the same nature acting on 2 bodies, same magnitude, in a pair. A exerts force on B, B exerts force on A.
Tension: opposite force on stationary object, balanced forces. use vector diagram and free body diagram.
Mass: amount of matter in a body.
Weight: gravitational force/gravity acting on an object. W = mg, W is weight (N), m is mass (kg), g is gravitational field strength (N/kg).
Gravitational field: region in which a mass experiences a force due to gravitational attraction.
Gravitational field strength: gravitational force acting per unit mass (10N/kg on earth).
Inertia: Reluctance of an object to change its state of rest or motion due to its mass.
Density: mass per unit volume. ρ = m/v, ρ is density (kg/m^3). m is mass (kg), v is volume (m^3).
Weighing machine: measures action force of object on weighing machine/reaction force of weighing machine on object, not mass/weight.
Moment: product of the force and perpendicular distance from the pivot to the line of action of the force. moment = Fd, moment (Nm), F is force (N), d is perpendicular distance (m).
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.
Centre of gravity: point through which an object's whole weight appears to act (pivot/directly below pivot in a body in equilibrium). punch 3 holes at the edge of the laminar, hang the laminar from a pin, hang a plumbline from the same pin, mark the vertical line made by the plumbline on the laminar, repeat for the 2 other holes, centre of gravity is at the intersection point of the 3 vertical lines. laminar should be free to turn about the pin, holes must be small so not too much of the laminar is removed.
Stability: measure of an object's ability to return to its original position after it is slightly displaced, stable equilibrium = object regains original position after displaced, unstable equilibrium = object moves further away when it is displaced, neutral equilibrium = object stays in new position when it is displaced, to increase stability, lower position of centre of gravity and increase base area.
Energy: capacity to do work.
Principle of Conservation of Energy: energy cannot be created nor destroyed, but can be converted from one form to another. the total energy in an isolated system is constant.
Energy transformations: battery (chemical potential -> electrical), radio (electrical -> sound), light bulb (electrical -> light + thermal), turbine (kinetic -> electrical).
Efficiency: efficiency = (useful energy output/total energy input) x 100%, efficiency (%), useful energy output (J), total energy input (J).
Work done: product of a constant force on an object and the distance* moved by the object in the direction of the force. W = Fx, W is work done (J), F is constant force (N), s is distance moved (m).
*if object is moving upwards, use vertical distance only (TBC). if object is moving sideways (height does not change), use horizontal distance. friction = frictional force x distance over which friction is exerted.
Kinetic energy**: KE = (1/2)mv^2, KE is kinetic energy (J), m is mass of body (kg), v is speed of body (m/s).
Gravitational potential energy**: GPE = mgh, GPE is gravitational potential energy (J), m is mass of body (kg), g is gravitational field strength (N/kg), h is height above ground (m).**gain in KE = loss in GPE, gain in GPE = loss in KE.
Power: rate of work done/energy conversion. P = W/t = E/t, P is power (W), W is work done (J), t is time taken (s), E is energy converted (J).
Pressure: force acting per unit area. p = F/A = hρg, p is pressure (Pa), F is force (N), A is area (m^2), h is height (m), ρ is density (kg/m^3), g is gravitational field strength (N/kg).
Hydraulic press: Fx x dx = Fy x dy, F is force exerted on piston (N), d is distance moved by piston (m)
Kinetic model of matter: tiny particles that make up matter are always in continuous random motion. Properties: particle arrangement (density), particle movement (volume, shape, compressibility).
Brownian motion: observed random movement of particles in a fluid, speed of particles increases with increased temperature, air particles bombard smoke particles continuously causing smoke particles to move continuously in random directions.
Gas: p ∝ T, p ∝ 1/V, V ∝ T, p is pressure (Pa), T is temperature (ºC), V is volume (m^3)
Light: speed in vacuum = 3 x 10^8m/s
1st law of reflection: incident ray, reflected ray and normal all lie in the same plane at the point of incidence.
2nd law of reflection: angle of incidence = angle of reflection. i = r, i is angle of incidence (º), r is angle of reflection (º).
Properties of image: same size, upright, laterally inverted, same distance behind the mirror as object is in front of the mirror, virtual.
Refraction: bending of light as it passes from one optical medium to another. n = c/v, n is refractive index, c is speed of light in vacuum, v is speed of light in medium.Refractive index: vacuum/air = 1, water = 1.33
1st law of refraction: incident ray, reflected ray and normal all lie in the same plane.
2nd law of refraction Snell's Law: for 2 given media, the ratio of the sine of the angle of incidence to sine of the angle of refraction is a constant. ni x sin(i) = nr x sin(r), i is angle of incidence (º), r is angle of reflection (º), n is refractive index.Critical angle: angle of incidence in an optically denser medium which the angle of refraction in the optically less dense medium is 90º. sin(c) = 1/n, c is critical angle (º), n is refractive index.
Total internal reflection: light ray travels from optically denser medium to optically less dense medium, angle of incidence is greater than critical angle.
Optical fibres: carry more information over long distance than copper wire, less signal loss, highly resistant to electromagnetic interference thus noise free.
Focal length = distance between the optical centre and focal point.
, f is focal length.
Wave: source = vibration/oscillation, transfer energy from one point to another without transferring the medium, transverse (travel perpendicular to direction of vibration) and longitudinal (travel parallel to direction of vibration).
Terms: amplitude = maximum displacement of a point from its rest position (m), wavelength = shortest distance between any two points in phase (crests and troughs, compressions and rarefactions) (m), period* = time taken to produce one complete wave (s), frequency* = number of complete waves produced per second and depends on source of the wave, wavefront = imaginary line on a wave that joins all adjacent points that are in phase.
*f = 1/T, f is frequency (Hz), T is period (s).Speed: distance travelled by a wave per second. v = λ/T = fλ, v is wave speed (m/s), λ is wavelength (m), T is period (s), f is frequency (Hz).
Water waves: reflection and refraction (shallow region, higher friction, lower speed, lower wavelength, towards the normal).
Visible light: red, orange, yellow, green, blue, indigo, violet (increasing frequency, decreasing wavelength).
Properties: transverse waves, do not require a medium to travel, travel at the speed of light in vacuum (3 x 10^8m/s), slow down in water or glass, no electric charge.
EM: radio waves (radio, television, navigation, radar), microwaves (satellite television, microwave oven), infrared radiation (television remote controllers, ear thermometer, intruder alarms, infrared heating), visible light (optical fibres, medical, telecommunication), ultraviolet radiation (sunbeds, fluorescent tubes, sterilisation of medical equipment), x-rays (hospital, produce x-ray images to diagnose fractures, tooth decay), gamma rays (treat cancer) (increasing frequency, decreasing wavelength).
Radiation: EM has the energy to remove electrons from atoms or molecules, exposure to ionising radiation can damage biological molecules and lead to abnormal cell division, cause cancers and deformities to a developing foetus (ultrasound is used).
Sound: form of energy that is transferred from one point to another as a longitudinal wave.
Speed: 330m/s, sonic boom = sound produced due to shock waves created due to compression of air when an object is travelling through air faster than sound, higher speed = stronger bonding between particles in the medium, solid then liquid then gas, higher elastic properties, higher temperature.
Echo: repetition of a sound due to the reflection of sound.
Ultrasound: sound with frequencies above the upper limit of the human range of audibility (20Hz to 20kHz), used for prenatal scanning, cleaning in dental treatment, detect cracks in metal structures.
Pitch: higher frequency = higher pitch.
Loudness: larger amplitude = louder sound.
Temperature: how hot or cold an object is.
Heat: amount of thermal energy that is being transferred from a hotter to colder region.
Ice point: pure melting ice RTP, 0ºC.
Steam point: pure boiling water RTP, 100ºC.
Calibrating thermometer: find position of ice point 0ºC, find position of steam point 100ºC, find the difference, divide by 100 to identify 1ºC. (θ-0)ºC = (position at θºC-position at 0ºC)/(position at 100ºC-position at 0ºC) x (100-0)ºC.
Thermometric properties: volume of mercury/alcohol, EMF, electrical resistance of metal, pressure of gas.
DONE! time is now 12.50am. time to sleep.
lynnette leong. siaoliao.