# A2 Physics

All the Topics in the A2 Physics Syllabus

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Physics January Revision.
Topic 2, Further Mechanics.
Linear Momentum.
Momentum is equal to mass times velocity and therefore the units are kilogram seconds to the minus one
or Newton seconds.
Momentum is a vector because velocity is a vector.
The principle of conservation of linear momentum states that in any interaction between bodies, linear
momentum is conserved provided no external force acts on the bodies.
The rate of change of momentum of an object is directly proportional to the resultant force which acts on
the object. Force is equal to change in momentum divided by time. Although if mass is constant force is
equal to mass times acceleration.
Impulse is equal to change in momentum. Impulse is equal to force times change in time.
In momentum collisions in 2 dimensions the component of the momentum in the x direction is conserved
and the component in the y direction is conserved.
Momentum and energy.
Energy cannot be created or destroyed. Energy can be transferred from one form to another but the total
amount of energy in a closed system will not change.
Kinetic energy is equal to half times the mass times the velocity squared. Kinetic energy is also equal to
momentum squared divided by 2 times mass.
Elastic potential energy is equal to half times k times the change in x squared.
Gravitational potential energy is equal to mass times gravity times the change in height.
In elastic collisions kinetic energy is conserved and momentum is always conserved. In inelastic collisions
kinetic energy is not conserved but momentum is always conserved.
Motion in a circle.
One radian is equal to 57.3 degrees.
To convert degrees to radians you times by pie over 180.
To convert radians to degrees you divide by pie over 180.
Angular velocity is the same as angular frequency and angular speed.
Angular speed is equal to angle turned divided by time.
Angular speed is also equal to 2 pie over time for one rotation.
Angular speed is also equal to 2 pie times frequency.
Linear speed is equal to angular speeds times the radius of the circle.

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Centripetal acceleration is equal to linear speed squared divided by the radius of the circle.
Centripetal acceleration is also equal to radius times the angular speed squared.
Centripetal acceleration is produced by the centripetal force and there are 2 equations for centripetal force.
Centripetal force is equal mass times velocity squared divided by radius.
Centripetal Force is also equal to mass times angular speed squared times radius.
If you remove the centripetal force the object would fly off at a tangent.

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Magnetic Fields.
A magnetic field is a region where a force is exerted on magnetic materials. Magnetic field lines go from
north to south. The closer together the lines the stronger the field,
There's a magnetic field around a wire carrying electric current. The direction of the magnetic field can be
worked out using the right hand rule.
The total magnetic flux passing through an area perpendicular to a magnetic field is equal to magnetic field

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Electromagnetic Induction.
Lenz's law states the induced e.m.f is always in such a direction as to oppose the change that caused it.
You can change the voltage induced in the coil by changing the following factors.
1. The angle between the coil and the field.
2. Number of turns of the coil.
3. Area of the coil.
4. Magnetic field strength (flux density).
5. Angular speed off the coil.
An alternator is a generator of alternating current.…read more

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De Broglie Wavelength is equal to Planck's constant divided by mass times velocity, where mass times
velocity equals momentum.
Electron volt is defined using accelerated charges. 1 electron volt is the kinetic energy carried by an electron
after it has been accelerated through a potential difference of 1 volt.
Energy gained by an electron in electron volts is equal to accelerating voltage.
The two linear accelerators are linear accelerator and the cyclotron. A
linac is a long straight tube containing a series of electrodes.…read more

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Quarks.
Quarks are fundamental particles. There are three types of quarks.
Up quarks have a plus two thirds charge.
Down quarks have a charge of minus a third. A
strange quark has a charge of minus a third.
There are three other types of quarks.
A top quark has a charge of plus two thirds. A
bottom quark has a charge of minus a third. A
charm quark has a charge of plus two thirds.…read more