Cheatography

# Unit 3 VCE Physics Cheat Sheet (DRAFT) by WhoooshBooosh

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``

### 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

### 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.

### 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

### 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)

### 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

### 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

### Projectile Range Formula

 R = u2sin(20) / g assuming symmetric motion