A2 Physics

Gravitational field strength at a point is the gravitational force per unit mass acting on a small mass placed at that point.

Newton’s law of gravitation states that the gravitational force between two point masses is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

Gravitational potential at a point is the work done per unit mass in bringing a small test mass from infinity to that point.

Escape velocity is the minimum speed that an object must have to escape from the gravitational field of a planet without further propulsion.

A geostationary orbit is an orbit in which a satellite remains fixed above a point on the Earth's surface, rotating with the same period as the Earth's rotation (24 hours).

Coulomb’s law states that the electrostatic force between two point charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.

Electric field strength at a point is the force per unit positive charge acting on a small test charge placed at that point.

Electric potential at a point is the work done per unit charge in bringing a small positive test charge from infinity to that point.

Capacitance is the ability of a system to store charge per unit potential difference between its plates. It is given by
C
=
Q
/
V
C=Q/V.

The time constant, τ, is the product of the resistance
R
R and the capacitance
C
C, and it represents the time taken for the charge or current to fall to 1/e (about 37%) of its initial value.

Faraday’s law states that the induced electromotive force (e.m.f.) in a circuit is directly proportional to the rate of change of magnetic flux linkage through the circuit.

Lenz’s law states that the direction of the induced e.m.f. is such that it opposes the change in magnetic flux that caused it.

Magnetic flux density is the force acting per unit current per unit length on a conductor placed at right angles to the magnetic field.

Magnetic flux through an area is the product of the magnetic flux density and the area perpendicular to the field:
Φ
=
B
×
A
Φ=B×A.

The r.m.s. value of an alternating current is the value of the direct current that would produce the same average power in a resistor as the alternating current.

The photoelectric effect is the emission of electrons from a metal surface when electromagnetic radiation of sufficient frequency (or energy) falls on the surface.

Einstein’s photoelectric equation is
E
=
h
f
=
ϕ
+
1
2
m
v
2
E=hf=ϕ+
2
1
​
mv
2
, where
E
E is the energy of the incident photon,
h
f
hf is the photon energy,
ϕ
ϕ is the work function, and
1
2
m
v
2
2
1
​
mv
2
is the kinetic energy of the emitted electron.

The work function is the minimum energy required to remove an electron from the surface of a material.

The de Broglie wavelength of a particle is given by
λ
=
h
/
p
λ=h/p, where
h
h is Planck’s constant and
p
p is the momentum of the particle.

Heisenberg’s uncertainty principle states that it is impossible to simultaneously determine the exact position and momentum of a particle with arbitrary precision. Mathematically:
Δ
x
Δ
p
≥
h
4
π
ΔxΔp≥
4π
h
​
.

Binding energy is the energy required to completely separate all the nucleons in a nucleus.

Einstein’s mass-energy equivalence principle is
E
=
m
c
2
E=mc
2
, which states that mass can be converted into energy and vice versa, where
E
E is energy,
m
m is mass, and
c
c is the speed of light.

Half-life is the time taken for half the number of radioactive nuclei in a sample to decay.

Specific latent heat is the amount of heat energy required to change the state of 1 kg of a substance without changing its temperature.

Boyle’s law states that the pressure of a fixed mass of gas is inversely proportional to its volume, provided the temperature remains constant.

Charles’s law states that the volume of a fixed mass of gas is directly proportional to its absolute temperature, provided the pressure remains constant.

The ideal gas equation is
P
V
=
n
R
T
PV=nRT, where
P
P is pressure,
V
V is volume,
n
n is the number of moles,
R
R is the gas constant, and
T
T is the absolute temperature.

The first law of thermodynamics states that the change in internal energy of a system is equal to the heat added to the system minus the work done by the system:
Δ
U
=
Q
−
W
ΔU=Q−W.

Internal energy is the total energy stored within a system, consisting of the kinetic and potential energies of the particles within the system.

Simple harmonic motion is the type of periodic motion in which the restoring force is directly proportional to the displacement and acts in the opposite direction.

The angular frequency in SHM is given by
ω
=
2
π
f
ω=2πf, where
f
f is the frequency.

Resonance occurs when a system is driven by an external force at its natural frequency, resulting in a large amplitude of oscillation.