Physics A2 Level

rate of change of momentum

mass times velocity

• First law: an object continues at rest or in uniform motion unless it is acted on by a resultant force
• Second law: the rate of change of momentum of an object is proportional to the resultant force on it
• Third law: when two objects interact, they exert equal and opposite forces on one another

the gravitational force F between two point masses m₁ and m₂ at distance r apart is given by F=Gm₁m₂/r²

force times time for which the force acts on an object

when two or more bodies interact, the total momentum is unchanged, provided no external forces act on the bodies

for a system of interacting objects is the total momentum of the objects remains constant provided no external resultant force acts on the system

the energy of a moving object due to its motion

when two objects fly apart, the two objects carry away equal and opposite momentum

a collision in which the total kinetic energy after the collision is equal to the kinetic energy before the collision

motion of an object moving at a constant speed along a circular path

the angle an object in circular motion turns through

the rate of change of angular displacement of an object in circular motion

for an object moving at speed v in uniform circular motion its centripetal acceleration a=v²/r towards the centre of the circle

the resultant force of an object that moves along a circular path

state of an object when at rest or in uniform motion

the maximum displacement from equilibrium of an oscillating object

distance in a given direction

oscillations where there is no damping and no periodic force acting on the system so the amplitude of the oscillation is constant

time taken for one complete cycle of oscillations

the number of cycles of oscillation per second

for an object oscillating at frequency f in simple harmonic motion its angular frequency = 2pif

motion of an object if its acceleration is proportional to the displacement of the object from equilibrium and is always directed towards the equilibrium position

forces that transfer energy which is wasted

• oscillations that reduce in amplitude due to the presence of resistive forces such as friction and drag
• 1.Lightly damped system: amplitude of oscillations decreases gradually
• 2.Heavily damped system: the system slowly returns to equilibrium without oscillating
• 3.Critically damped system: system returns to equillibrium in the least possible time without oscillating

a force that varies regulary in magnitude with a definite time period

the frequency of free oscillations of an oscillating system

oscillations of a system that is subjected to an external periodic force

the amplitude of vibration of an oscillating system subjected to a periodic force is largest when the periodic force has the same frequency as the resonance frequency of the system

the frequency of an oscillating system in resonance

the region surrounding an object in which it exerts a gravitational force on any other object

a line followed by a, small mass in a gravitational field/ a small positively charged object in an electric field/ a free north pole in a magnetic field, acted on by no other forces than the force due to the field

a field in which th field lines are straight and converge or diverge as if from a single point

a region where the field strength is the same in magnitude and direction at every point in the field

the work done per unit mass to move a small object from infinity to that point in a gravitational field

the work done to move a small object from infinity to that point in the field

• at a point in a field is the change of potential per unit charge of distance along the field line at that point
• -the field strength at any point

the force per unit mass on a small mass placed in the field

an attractive force that acts equally on any two objects due to their mass

for any planet, the cube of its mean radius of orbit is directly proportional to the square of its time period

the constant of proportionality in Newton's law of gravitation

an object that can conduct electricity

electrons in a conductor that move about freely inside the metal because they are not attached to a particullar atom

a device used to detect electric charge

a material that cannot conduct electricity

the force per unit charge on a small positively charged object at a point in an electric field

the work done per unit charge on a small positively charge object in an electric field to ove it from infinity to that point in the field

a line or surface in a field along which the electric or gravitational potential is constant

• for two point charges Q1 and Q2 at distance apart r, the force between the two charges
• 

• the charge stored per unit pd of a capacitor
• unit- farad (F)= 1 coulomb per volt

the time taken for a quantity that decreases exponentially to decrease to 0.37 (=1/e) of its initial value

energy stored by the capacitor

through a fxed resistor of resistance R, time constant= FC

the force on a current-carrying conductor due to a magnetic field

rule that relates the directions of the force, magnetic field and current on a current-carrying conductor in a magnetic field

the magnetic force per unit length per unit current on a current carrying conductor at right angles to the field lines

an electric motor with an armature consisting of a single coil of insulated wire

a device used to measure magnetic flux density

the generation of an emf when magnetic flux linkage through a coil changes or a conductor cuts across magnetic field lines

rule that relates the directions of the induced current, magnetic field and velocity of the conductor when the conductor cuts across magnetic field lines and an emf is induced in it

when a current is induced by electromagnetic induction, the direction of the induced current is always such as to oppose the change that causes the current

equals BA for a uniform magnetic field of flux density B that is perpendicular to an area A

through a coil of N turns, = NBA

the induced emf in a circuit is equal to the rate of change of magnetic flux linkage through the circuit

• converts the amplitude of an alternating pd to a different value
• it consists of two insulated coils, the primary and secondary coil, wound round a soft iron laminated core

a transformer in which the rms pd across the secondary coil is less than the rms pd applied to the primary coil

a transformer in which the rms pd across the secondary coil is greater than the rms pd applied to the primary coil

the ratio of the secondary voltage to the primary voltage is equal to the ratio of the number of secondary turns to the number of primary turns

for an ideal transformer the output power equals the input power

unwanted induced currents in the metal parts of ac machines

the network of transformers and cables that is used to distribute electrical power from power stations to users

• emf induced in the spinning coil of an electric motor or in any coil which the current is changing
• acts against applied p.d.