AS Level Physics Definitions Flashcards
Scalar
A quantity that has a magnitude only.
vector
A quantity that has both magnitude and direction.
precision
The degree of agreement between several measurements of the same quantity, determined by the range of the values.
accuracy
The closeness of measurement values to the true values.
systematic error
The type of error that causes readings to deviate in one direction from the true value.
random error
The type of error which causes readings to scatter about the true value.
distance
Total length covered irrespective of the direction of motion.
displacement
Distance moved in a certain direction from start to end point.
speed
Distance travelled per unit time.
velocity
The rate of change of displacement.
acceleration
The rate of change of velocity.
mass
A property of a body that resists change in motion.
linear momentum
The product of mass and velocity.
force
The rate of change of momentum.
Newton’s First Law
A body continues in a state of rest or constant velocity unless acted upon by a resultant force.
Newton’s Second Law
The resultant force is equal to the rate of change of momentum and acts in the direction of it.
Newton’s Third Law
Every action has an equal and opposite reaction.
Impulse
The product of the force and the time during which the force acts.
Weight
The effect of gravitational field on a mass.
Principle of conservation of momentum
For a system of interacting bodies, the total momentum remains constant provided there is no resultant force acting on the system.
Elastic collision
Both momentum and kinetic energy are conserved.
Inelastic collision
Only momentum is conserved; total kinetic energy is not conserved.
moment
The product of the force and the perpendicular distance of its line of action to the pivot.
torque of a couple
The product of one force in a couple and the perpendicular distance between the forces.
principle of moments
For a body in equilibrium, the sum of all anti-clockwise moments about a point equals the clockwise moments about that same point.
pressure
The force per unit area.
density
The mass per unit volume.
power
The work done per unit time.
Centre of Gravity
The point through which the entire weight of a body may be considered to act.
Work Done
The product of force and displacement in the direction of the force.
Efficiency
The ratio of useful energy output from the system to the total input energy.
Gravitational Potential energy
Energy of a mass due to its position in a gravitational field.
Kinetic energy
Energy a mass has due to motion.
Elastic potential energy
Energy stored in an object due to a force changing its shape.
Stress
The force per cross-sectional area.
Strain
The ratio of extension (change in length) to original length.
Young’s Modulus
The ratio of stress to strain.
Elastic limit
The point beyond which a material does not return to its original length when the load is removed.
Displacement of a wave
The distance of a point on a wave above or below the equilibrium position.
Hooke’s Law
Force is proportional to extension provided the proportionality limit is not exceeded.
Amplitude
The maximum distance of a particle in a wave measured from the equilibrium position.
Frequency of a progressive wave
The number of wavefronts passing a point per unit time.
Frequency of a source
Number of oscillations per unit time from the source of the wave.
Wavelength
The minimum distance between two adjacent crests or troughs.
Speed of a wave
The speed at which energy is transferred/ speed of a wavefront.
Progressive wave
A wave that transfers energy as a result of vibrations.
Transverse wave
A wave where the vibration of particles is perpendicular to the direction of propagation of energy.
Longitudinal wave
A wave where the vibration of particles is parallel to the direction of propagation of energy.
Doppler effect
The observed frequency is different from the source frequency when the source moves relative to the observer.
Principle of superposition
When two waves meet, the resultant displacement is the algebraic sum of the individual displacements.
Diffraction
When a wavefront is incident on a gap, the wave spreads.
Antinode
A point of maximum amplitude on a standing wave.
Node
A point of zero amplitude on a standing wave.
Interference
Same as superposition.
Coherence
Constant phase difference between two waves.
Formation of a stationary wave
When two waves, having the same frequency and wavelength, traveling in opposite directions meet, the resultant displacement is the sum of the individual displacements of the waves, and produces nodes and antinodes.
Conditions for interference
- Two waves meet 2. Waves have a constant phase difference.
Electric current
The flow of charge carriers.
Coulomb
The charge of an ampere second.
Potential difference
the work done per unit charge.
Electromotive force
The total energy transferred by a source in driving a unit charge round a complete circuit.
Electrical Resistance
The ratio of potential difference across a component to the current flowing through it.
Ohm
The resistance of 1 volt per ampere.
Ohm’s law
The current in a metallic conductor is directly proportional to the potential difference across its ends, provided its temperature remains constant.
Kirchhoff’s first law
The algebraic sum of currents entering a junction is zero.
Kirchhoff’s second law
In a closed circuit, the sum of e.m.f’s is equal to the sum of p.d’s.
Volt
Joule per coulomb.
Difference between p.d and emf
Potential difference (p.d.) is the energy transformed from electrical to other forms, per unit charge. Electromotive force (e.m.f.) is the energy transformed from other forms to electrical per unit charge.
Internal resistance
Resistance in the battery causing loss of volts.
