AS Definitions and Laws Flashcards
Acceleration
Rate of change of velocity.
Recall formula: a = Δv/Δt
Accuracy
Measurement is accurate if it is close to the true value.
Alpha particle
A helium nucleus.
Has 2 protons and 2 neutrons.
Stopped by paper.
Most ionising.
Amplitude
Maximum displacement from the equilibrium position to the crest.
Antinode
Point of maximum displacement in a stationary wave.
Base quantities
Physical quantities that are used to define other physical quantities. mass length, time temperature current amount of substance
Base units
Units of base quantities; kg m s K A mol.
Beta particle
A fast moving electron or positron.
Stopped by a few cm of aluminium.
Less ionising compared to alpha particle.
Centre of gravity
Point at which the whole weight of the body may be considered to act.
Coherence
- Constant phase difference between waves.
2. Waves have same frequency.
Constructive interference
Occurs when two waves are in phase. Condition for constructive interference: Path difference = n(lambda), where n = 0, 1, 2, …... or Phase difference = n x 2(pi) radians.
coulomb (C)
1 C of charge passes a point when a current of 1 A flows for 1 s.
(Recall formula: Q = It)
Couple
Two parallel forces which are equal but opposite. Their lines of action do not meet.
Current
Rate of flow of charged particle.
Recall formula: Q = It
Density
Mass per unit volume.
Recall formula: density = M/V
Destructive interference
Occurs when the two waves are out of phase.
Condition for destructive interference:
Path difference = (n + ½)lambda, where n = 0, 1, 2, ……
or
Phase difference = (n + ½)(2 x pi) radians
Diffraction
The spreading out (or bending) of waves when they pass through a gap (or when they pass the edge of an object).
Diffraction grating formula
n(lambda) = d sin (theta)
Diode
A device that allows current to flow through it in one direction only.
Displacement
Distance from a fixed point in a specified direction.
Ductile material
A material that can be drawn into a thin wire without breaking.
Efficiency
Efficiency = useful energy output/ total energy input
or
Efficiency = useful power output/ total power input
Elastic deformation
When a force is applied, the material changes its shape/ size. When the force is removed, the material returns to its original shape/ size.
Elastic collision
A collision in which momentum and kinetic energy are conserved.
Total k.e. before collision = total k.e. after collision.
In a perfectly elastic collision,
relative speed of approach = relative speed of separation.