Show Menu
Cheatography
  1. Home >
  2. Education >

Unit 3 VCE Physics Cheat Sheet (DRAFT) by

For year 12 VCE Physics class, unit 3 exam.

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Newton's Laws of Motion

First Law:
Objects have inertia, i.e. a stationary object remains statio­nary, or a moving object keeps on moving at the same speed in the same direction, if there is no net force acting on it
Second Law:
Accele­ration of an object is directly propor­tional to and in the same direction as the net force on it, and inversely propor­tional to its mass.
F
net
= ma
Third Law:
When object A exerts a force on object B, B exerts a force of the same magnitude in the opposite direction on A .
F
on A by B
= -F
on B by A

Vector Addition

SLM Constant Accele­ration Equations

Uses:
Equation
v u a t
v = u + at
v u t s
s = 1/2 (u + v) t
u a t s
s = ut + 1/2 at2
v a t s
s = vt - 1/2 at2
v u a s
v2 = u2 + 2as

Interp­reting Motion Grpahs

 
d - t
v - t
a - t
Direct Reading
d at any t
t at any d
v at any t
t at any v
a at any t
t at any a
Gradient
intsan­taneous velocity at any point
v
avg
between any two points
instan­taneous accele­ration
a
avg
-
Area under graph
-
change in position
change in velocity

Einstein's Special Relativity

Postulate One
The Principle of Relativity
Postulate Two
The Constancy of the Speed of Light
the laws of physics are the same in all inertial frames of reference (not just mechanics)
the speed of light is constant for all observers
there is no 'prefe­rred' or 'correct' frames of reference
this implies a universal speed limit
 
this has implic­ations of simult­aneity of events

Time Dilation

t = t
0
γ
γ = 1 / √*1 - v2/c2
t
0
 is proper time, t is dilated time (larger than proper time), γ is the Lorentz Factor

Length Contra­ction

L = L
0
/γ = L
0
√1 - v2/c2
L
0
is proper length, L is contracted length (small than proper length), and γ is still Lorentz factor

Relati­vistic Energy

Magnetic Flux and Induced EMF

AC Generators (Alter­nators)

Induced EMF and Energy

Lenz's Law

Transf­ormer Equations

Across step-up and step-down transf­ormers
V
1
/ V
2
= N
1
/ N
2
= I
2
/ I
2
Where voltage and no. of turns are propor­tional to each other and current is inversely propor­tional.

DC Generators

  

Circular Motion

Centri­petal Accele­ration

1. Draw diagram showing all forces
2. If required, resolve forces into components
3. There is always a net force towards centre of circular path
Useful equations:
F
net
= mv2 / r
v = 2πr / T
a = v2 / r = 4πr2 / T = 4π2f2r

Motion at Bottom of Loop

Motion at Top of loop

Energy

Conser­vation of Energy
in an isolated system, energy is transf­ormed from one form to another, can neither be created nor destroyed
E
k
= 1/2mv2
E
g
= mgΔh
Hooke's Law
force exerted by spring is directly propor­tional, but opposite in direction, to the spring's extension or compre­ssion
F
s
= -kx
Strain Potential Energy
E
s
= 1/2kΔx2

Gravity

Newton's Law of Universal Gravit­ation
Gravit­ation is a force of attraction that acts between any two bodies. The gravit­ational force between two bodies is given by:
F = GMm/r2 = mg
Gravit­ational Fields
Vector field, a physical quantity with value at each point in space, existing in any region with gravit­ational effect
g = f/M = GM/r2 (N kg-1) = a(m s-1)
Free Falling Objects
influenced only by gravity
net force given by: ΣF = mg
a = ΣF/g = mg/g = g
Kepler's Law
R3/T2 = GM/4π2
Work done
objects moving through constant gravit­ational field
E
g
= mgΔh
total energy of object moving through gravit­ational field is constant, even though relative amounts of kinetic and gravit­ational potential energy may change
area under gravit­ational field-­dis­tance graph gives energy change per kilo of mass

Electr­icity

Electric Fields
vector fields occurring around charged objects
fields exert a non-co­ntact force, may be attractive or repulsive
Force on Charged Particle
F = qE
Coulomb's Law
The electric force between two charges (q1, q2) is propor­tional to the product of the charges and inversely propor­tional to the square of the distance between them.
Point Charges
F = kq
1
q
2
/ r2
where a positive value of force represents repulsion
E = kQ / r2 (N C-1)

DC Motors (Split Ring Commut­ators)

Wein Filter

Changing the flux by rotating a loop

Root Mean Square Voltage

Projectile Motion

  

Momentum

"mass in motion­"
p = mv
is a vector
F
net
= Δp / Δt
A net force on an object will cause a change in momentum (Impulse)

Conser­vation of Momentum

If two objects collide in an isolated system, momentum will be conserved
initial momentum = final momentum
Σp
initial
= Σp
final
m
1
u
1
+ m
2
u
2
= m
1
v
1
+ m
2
v
2
OR Σp
final
- Σp
initial
= Δp = 0

Impulse

Impulse = F
net
Δt = mΔv = Δp
is a vector
units are either N s-1 OR kg m s-1
using this equation between two states gives us the average F
net
is area under force-time graph

Collisions

An isolated event (no external forces and momentum is conserved) involving 2 or more objects
Elastic Collision momentum and energy is conserved
Usually interact (often strongly) for a short period of time
Inelastic Collision momentum is conserved but energy is not (lost to usually heat and sound)
Equal and opposite impulses are exerted on each other

Work

Work(s­calar) is the energy transf­erred to an object or transf­ormed by the applic­ation of a force
Work is done by a force on an object when it causes a displa­cement of an object in the direction of the force
W = Fs
W = Fs cosθ*
Work done on an object:
W = F
net
s
If the energy doesn't change, or force is perpen­dicular to displa­cement, no work is done on object
is area under force-­dis­pla­cement graph

Magnets

Magnetic FIelds
vector fields, denser the lines means stronger the fields
field lines go from north to south pole and never touch
magnets are always dipole, can never be monopole
Earth as a Magnet
The Earth is one large magnet – believed to be due to convection currents of molten metals in the outer core
True geographic north pole is actually magnetic south pole

Induced EMF in a Moving Conductor

Linear Particle Accele­rators

Charged Particles in a Magnetic Field

Generating Voltage

We know electric currents can produce magnetic fields
The separation of charges in the falling rod is an induced electr­omotive force or induced voltage (or potential differ­ence)
The object needs to keep moving, or the magnetic field needs to be changing for charges to remain separated (to maintain an induced voltage)
Electr­omotive force (emf), is a source voltage

Transf­ormers

Inclined Plane

Banked Turn Design Speed

Projectile Motion

Projectile Range Formula

R = u2sin(20) / g
assuming symmetric motion