2013 HSC COURSE

interrupts the discussion or discourse and addresses directly a person or personified thing, either present or absent. Its most common purpose in prose is to give vent to or display intense emotion, which can no longer be held back:

a statement or proposition that seems self-contradictory or absurd but in reality expresses a possible truth.

an informally-stated syllogism which omits either one of the premises or the conclusion.

consists of arranging words, clauses, or sentences in the order of increasing importance, weight, or emphasis

repetition of one word (for emphasis):

quoting a maxim or wise saying to apply a general truth to the situation

Spacing / distance between actors enabling audience to establish relationship

The moving and positioning of actors

Occurs when an object is subject to a centripetal force. Fc = (mV^2)/r. A centripetal force is a force perpendicular to the velocity of the object causing it to constantly change direction so that it follows a circular path. The force thereby is always directed towards the centre of motion.

ball on a string whirled in a circle - source is tension in the string. Car driving around a roundabout - source is friction between the tyres and the road. Satellite orbiting the earth - source is gravitational attaction between satellite and earth.

Low earth orbit (orbit between 250 - 1000km), geostationary (P = Pearth = 24h following the equator), geosynchronous (P=24 hours passing over but not following the equator appears like a figure 8 from the ground), transfer orbit (path used to manoeuvre a satellite from one orbit to another)

6.67 x 10^-11 n(kg/m)^2

LEO: v: bigger. P: smaller. r: smaller: Signal: stronger lifespan: shorter GEO: v: smaller. P: bigger. r: bigger. signal: weaker. lifespan: larger

The instantaneous speed of an object in orbit in the direction indicated by an arrow (directional) drawn as a tangent to the point of interest on the orbital path. r^3/t^2 = (Gm)/(4π^2) (keplers law of periods) and Vorbital = root((Gm)/r) V = (2πr)/t

occurs in satellites in low earth orbit. LEO are subject to friction with the outer fringes of the atmosphere. Friction = loss in energy of the satellite. as such the orbit is no longer viable so the satellite will drop down to a new viable orbits that corrosponds with the lesser energy. Orbital velocity increases therefore Ek increases (some of the Ep ---> Ek). Orbital decay is cyclical - with the decreased r of the satellite it will experience more friction and the process will repeat itself over and over.

heat, g-forces, radio blackout, landing

As the space craft reenters the atmosphere friction with the molecules in the atmosphere cause the craft to decellerate. The energy from the friction is converted to high amounts of heat. This is combatted through the use of heat shields that use either ablative surfaces (e.g. apollo capsule) or insulating surfaces (e.g. spaceshuttles). Heat can also be minimised by entering at the optimum angle of reentry and having a blunt nosed spacecraft (heat is distributed more evenly over the craft).

decelleration of the space craft as it reenters produces high g forces. These can be tollerated by reclining the astronaut so the bloods is not forced away from the brain and fully supporting the body face up. G-forces can also be minimised through reentering at the optimum angle. May also be minimised by g suits (suits with inflatable bladders to restrict the draining of blood away from the brain.

For a certain time period in reentry overheated air particles ionise as they collide with the craft thereby causing a radio blackout. The effect of this is minimised by allowing control of the craft to be independant of the ground control and training the crew to deal with this.

spacecraft has to lose further Ek in order to touchdown safely. Solutions include: deployment of parachutes then touchdown in water or on ground and landing on an airstrip using air brakes, s turns etc... (space shuttle)

For all reentries there is an optimum angle. e.g. apollo 5.2-7.2 degrees. e.g. spaceshuttle ~40 degrees. If the angle is too shallow then the craft will rebound due to the compression of the atmosphere If the angle is too steep then the craft will decellerate too quickly resulting in it burning up.

1. altitude. height about the surface of the planet affects the strength of gravity. g = (Gmp)/(rp + alt)^2 2. variations in gravity due to the earths crust. The earth's crust is not uniform - density and thickness distribution is not even. 3. variations in radius. The earth is an ellipsoid not a perfect circle - it is flattened out at the poles therefore g at the poles is less than the equator. 4. Because the earth rotates there is a centripetal force acting providing a pulling force towards the centre of the earth. Therefore properly g = (Gm)/r - ac.

The strength of a gravitational field is proportional to its mass and inversely proportional to the square of the distance between the centre of the object providing the field and the object the field is impacting upon. g = (Gm)/r

Every object in the universe attracts every other object with a force directed along the line between the centres of the 2 that is directly proportional to the product of their masses and inversely proportional to the suare of the the distance between the centres of the 2. F = (Gm1m2)/r^2

Circular motion is a result of a centripetal force (a force acting perpendicular to the velocity of an object). In satellites this centripetal force is provided by the gravitational force between the satellite and the object it is orbiting i.e. Newtons's law of universal gravitation F = (Gm1m2)/r^2

Also know as planetary assist or gravity assist. By utilising the gravitational force of the planet on the craft and the motion of the planet the slingshot effect changes the velocity of a spacecraft relative to the sun and to changes the direction of an object.e.g. if the space craft enters behind the planets motion it will accelerate due to the planets gravity, speeding up and then decellerate, slowing down - the velocity of the craft relative to the planet will be unchanged. However because the planet is rotating around the sun the craft is "dragged along" with it increasing its speed greatly relatively to the sun. This increase in rel velocity saves fuel for the craft and therefore money and also increases the crafts acceleration by decreasing its total mass. This makes larger / further space flights more possible

19th century physists believed that light was a wave form and therefore like all other known wave forms that it required a medium for propegation. No medium could be found and therefore the aether was hypothesised. The aether's properties included: 1.filled all space. 2. had great elasticity in order to propegate light. 3. was perfectly transparent. 4. could permeate all matter 5. had low density. 6. was stationary in space.

The Earth moves about the sun at ~30kms^-1. According to the aether model the earth moves through the aether. Therefore from the earth's frame of reference we should experience an aether wind.

The michaelson morley experiment was an experiment used to predict the speed of the earth relative to the aether and hence determins the aether's existance. It used an interferometer (the interferance of light rays) and the 'aether wind'.

The experiment had a light source directing light rays at a 1/2 silvered 1/2 transparent mirror positioned at a 45 degree incline. The mirror would split the light ray into 2 seperate rays one going through the mirror and the other reflected upwards. Both the rays hit seperate mirrors reflecting back towards the hald silvered half transparent mirror and then into a telescope. The entire experiment is on a rotating platform

The 2 light rays were expected to return at different times due to the aether wind (crossing should be faster than going up and down) and from the different distances travelled by the rays resulting in a light pattern. This should be emphasisesd through the ability of the experimenter to rotate the platform thereby shifting the patten (from changing the angle between the rays and the aether wind)

The pattern on the telescope did not shift as expected - the experiment achieved a null result however the aether theory was not disproved

The michaelson morley experiment achieved a null result however the theory was not disproved. Various modifications to the aether theory each with their own set of expectations were tried and failed. 20 years after the experiment: Einstein's theory of relativity in which c was constant, space and time were relative and the aether model was superflous. The theory of relativity had its own set of predictions not all of which were able to be proved at the time, however these have been proved now. Choices for scientists were 1. Follow the aether model in which no predictions were found true or 2. follow the theory of relativity in which all predictions were proved.

An inertial frame of reference is a rigid frame in which v,r etc can be measured. It is a non accelerated environment (i.e. steady or no motion relative to an outside observer) where the laws of physics (inc relativity inc inertia) hold