definitions Flashcards
Systematic errors
Result in all readings or measurements being always smaller or larger than the true value by a fixed amount
Random errors
Results in readings or measurements being scattered about a mean value. These errors have equal probability of being positive or negative
Accuracy
degree of closeness of the mean value of the measurements to the true value
it is affected by systematic error
Precision
degree of agreement between repeated measurements of the same quantity
it is affected by random error
Newtons first law
every object continues in its state of rest or uniform motion in a straight line unless an external resultant force acts upon it
Newtons second law
rate of change of momentum of a body is proportional to the resultant force acting on it and the change occurs in the direction of the force
Newtons third law
if body A exerts a force on body B, then body B exerts an equal but opposite force on body A
Principle of conservation of momentum
when a system of bodies interact the total momentum of the system remains constant provided no net external force acts on it
Impulse
product of the force acting on an object and the time for which the force acts
Momentum
product of the mass of an object and its velocity
Hookes law
extension of a spring is proportional to the applied force if the limit of proportionality is not exceeded
Centre of gravity
point through which the line of action of the entire weight of a body appears to act
Pressure
normal force acting per unit area, where the force is acting at right angles to the area
Upthrust
vertical upwards force exerted on a body by a fluid when it is fully or partially submerged in the fluid due to the difference in fluid pressure
Principle of floatation
For an object floating in equilibrium, the upthrust is equal in magnitude and opposite in direction to the weight of the object
Moment
of a force about a point is defined as the product of the force and the perpendicular distance from the point to the line of action of the force
Principle of moments
For a body in rotational equilibrium, the sumo f all the clockwise moments about any axis must equal the sum of all the anticlockwise moments about the same axis
Work done
by a constant force is the product of the force and the displacement in the direction of the force
Energy
the capacity to do work
Law of conservation of energy
energy cannot be created or destroyed. it can only be converted from one form to another
Power
rate of work done or energy conversion with respect to time
Angular displacement
angle an object makes with respect to a reference line
Angular velocity
rate of change of its angular displacement wrt time
Period
time taken for an object/particle of a wave to make 1 complete revolution/oscillation
Frequency
number of revolutions/oscillations made per unit time
Newtons law of gravitation
states that 2 point masses attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them
Gravitational field
region of space in which a mass placed in that region experiences a gravitational force
Gravitational field strength
at a point in space is defined as the g force experienced per unit mass at that point
Gravitational potential energy
of a mass at a point in a g field is the work done by an external force in bringing the mass from infinity to that point
Escape velocity
minimum speed needed for the object to just escape from the g influence of a massive body
Gravitational potential
at a point in a g field is the work done per unit mass by an external force in bringing a small test mass from infinity to that point
Geostationary satellite
remains in a fixed position in the sky when viewed from any location on Earths surface
Simple Harmonic motion
motion of a particle about a fixed point such that its acceleration is proportional to its displacement from the fixed point and is always directed towards the point
Angular frequency
rate of change of phase angle of the oscillation and is equal to the product of 2pi and its frequency
Amplitude
magnitude of the max displacement of the particle (in a wave) from its eqm position
Free oscillation
occurs when an object oscillates with no resistive and driving forces acting on it. its total energy and amplitude remain constant with time
Forces oscillations
body is subjected to a periodic external driving force and made to oscillate at the frequency of the driving force, which may not be its natural frequency
Resonance
System responds at max amplitude to an external driving force. this occurs when the freq of the driving force is equal to the natural freq of the driving system
Progressive waves
transports energy from one point to another in the direction of wave propagation
Displacement
distance in a specific direction of a particle of a wave from its eqm position
Phase angle
angle that gives a measure of the fraction of a cycle that has been completed by an oscillating particle or by a wave (e pi is one full oscillation)
Phase difference
between 2 particles in a wave/between 2 waves at a point is a measure of the fraction of a cycle which one is ahead of the other
Wavefront
line or surface joining points on a wave that are in phase (wave travels perpendicular to the wavefront)
Intensity
rate of transfer of energy per unit area normal to the direction of the energy transfer of the wave
Transverse wave
particles oscillate in a direction perpendicular to the direction of energy transfer
Longitudinal waves
particles oscillate in a direction parallel to the direction of energy transfer
Polarisation
oscillations of the wave particles in a transverse wave are restricted to one direction only and this direction is perpendicular to the direction of energy transfer
Malus Law
intensity of a beam of plane polarised light after passing through a polariser varies with the square of the cosine of the angle through which the polariser is rotated from the position that gives max intensity
Superposition
when 2 or more waves of the same type meet at a point in space, the resultant displacement at that point is equal to the vector sum of the displacements of the individual waves at that point
Stationary waves
result of the superposition of 2 progressive waves of the same type, frequency, amplitude and speed, travelling along the same line but in opposite directions
Antinode
point in a stationary wave where amplitude is the max
Node
point in a stationary wave where amplitude is 0
Diffraction
bending of waves after passing through an aperture or round an obstacle
Coherence
waves are coherent when they have a constant phase difference (same freq)
Interference
superposition of 2 or more waves to give a resultant wave whose resultant amplitude is given by the principle of superposition
Constructive interference
when 2 coherent waves arrive at the same point with a phase difference of 0 to produce a maximum
Destructive interference
when 2 coherent waves arrive at the same point with a phase difference of pi to produce a minimum
Path difference
diff in the distance that each wave travels from its source to the point where they meet
Rayleigh criterion
states that 2 images are just resolved by an aperture when the central max of the diffraction pattern of 1 image falls on the 1st minimum of the diffraction pattern of the other image
