# Physics Study Notes Hsc

**Topics:**Special relativity, General relativity, Force

**Pages:**71 (19481 words)

**Published:**November 26, 2012

Core Topic Two: Motors and Generators 1. 2. 3. 4. 5. The Motor Effect Electromagnetic Induction Electric Generators Transformers Electric Motors 19 24 27 29 31

Core Topic Three: From Ideas to Implementation 1. 2. 3. 4. Cathode Rays Quantum Theory Solid State Devices Superconductivity 32 37 43 48

Option Topic: Quanta to Quarks 1. 2. 3. 4. 5. 6. Models of the Atom Quantum Physics The Electron Microscope Applications of Radioactivity Nuclear Applications The Structure of Matter 53 57 59 61 66 67 William Kim HSC Physics Summary | page 1

Core Topic One: Space 1. The Earth has a gravitational field that exerts a force on objects both on it and around it § Define weight as the force on an object due to a gravitational field The weight of an object is the force of gravity acting on it. r r W = mg Where W is the weight in newtons (N), m is the mass in kilograms (kg) and g can be either: 1. The acceleration due to gravity (= 9.8 m/s/s at the Earth’s surface); or 2. The gravitational field strength (= 9.8 N/kg at the Earth’s surface). §

Define gravitational potential energy as the work done to move an object from a very large distance away to a point in a gravitational field.

As we lift an object from the ground to a height above the ground we do work on it. This work is stored in the object as gravitational potential energy. For an object of mass m at a height h above the Earth’s surface the gravitational potential energy E is given by: E p = mgh However this equation is valid only when the object is near the Earth’s surface. The gravitational potential energy is a measure of the work done in moving an object from infinity to a point in the field. The general expression for the gravitational potential energy of an object of mass m at a distance r from the centre of the Earth (or other planet) is given by: E p = −G mM E r

Newton’s Law of Universal Gravitation

mm F = G 12 2 r where G is the universal gravitational constant. The Gravitational Field Surrounding any object with mass is a gravitational field. g= Gm r2

Where M is the mass of the Earth (or other planet).

Change in Gravitational Potential Energy The change in potential energy of a mass m1 as it moves from infinity to a distance r from a source of a gravitational field (due to a mass m2) is given by: mm ∆E p = G 1 2 r Change in Gravitational Potential Energy Near the Earth (when radius increases from A to B)

1 1 ∆E p = GmM E − r A rB

William Kim HSC Physics Summary | page 2

2. Many factors have to be taken into account to achieve a successful rocket launch, maintain a stable orbit and return to Earth § Describe the trajectory of an object undergoing projectile motion within the Earth’s gravitational field in terms of horizontal and vertical components Any moving object that moves only under the force of gravity is a projectile. The horizontal motion of a projectile is independent to the vertical motion. The reason for this result is that gravity is the only force acting on the objects and this always acts towards the centre of the Earth. Projectile motion can be analysed by realising that: 1. The horizontal motion is constant velocity. 2. The vertical motion of constant acceleration (with acceleration of g). Equations of Uniformly Accelerated Motion r r r v = u + at r r 1r s = ut + at 2 2 2 2 v = u + 2 as The Path of a Projectile The velocity at any point of the path of a projectile is simply the vector sum of the horizontal and vertical velocity components at that point. ∆y = k (∆x ) 2 ag k = 2 2u x The horizontal component is constant. The vertical component changes at g, the acceleration due to gravity. Trajectories The path followed by a projectile – its trajectory – is a parabola (or linear) (1) Horizontal motion: ∆x = u x t 1 (2) Vertical motion: ∆y = a g t 2 2...

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