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# AS and A Level: Waves & Cosmology

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## Redshift

1. 1 When a source of waves is moving relative to an observer (either towards or away) the received waves have a different wavelength to the wavelength transmitted. This is known as the Doppler Effect and we can use it to calculate the speed of a galaxy relative to Earth.
2. 2 Almost all galaxies show redshift, meaning that the wavelength received on Earth is longer than it was when transmitted. It’s called redshift because the wavelength received has moved towards tor even beyond the red end of the spectrum . Redshift implies that the galaxy is moving away from Earth.
3. 3 Blueshift can be observed from ‘nearby’ stars and galaxies.

## Hubble's law

1. 1 Using redshift data from a number of galaxies, Hubble plotted a graph of recession velocity, v, against distance to the galaxy, d. This graph continues to be updated and it shows that v = Hod which is known as Hubble’s law. This means that the speed of recession is directly proportional to the distance to the galaxy.
2. 2 Ho is the Hubble constant and it has a value of about 70 km s-1 Mpc-1, which is equivalent to 2.3x10-18 s-1. 1/Ho= 4.4 x1017 s = 1.4 x 1010 years! This is the age of the universe, about 14 billion years.
3. 3 We can also find an estimate for the size of the (visible) universe, assuming that the maximum expansion speed is the speed of light. Using Hubble law, c = Hod so d = c/Ho = 14 billion light years.
4. 4 The uncertainty over the value of The Hubble constant is becoming smaller as measurements of distance to galaxies improve
5. 5 Since redshift is seen in every direction, the conclusion is that the universe is expanding.

## Fate of the universe

1. 1 The fate of the universe is closely linked to CRITICAL DENSITY. This is a theoretical density that would have enough mass in the universe to keep the expansion of space slowing down forever. The critical density is given by o= 3H2/8 . The universe would be FLAT. An accurate value for H is important, if we want an accurate value for the critical density. Note: H2 means that the percentage uncertainty in H has to be doubled.
2. 2 If the actual density is greater than the critical density, then the universe will stop expanding at some point and then collapse. The universe is then CLOSED. This outcome is known as the Big Crunch.
3. 3 If the actual density is less than the critical density, there is not enough mass to stop the expansion and the universe will continue to expand forever. The universe is OPEN.
4. 4 Determining the actual density is difficult because there seems to be dark matter which we cannot yet detect directly but which can be inferred by the gravitational effects it has. e.g the rotation of galaxies is not consistent with observable mass but with increased mass that may be explained by the presence of dark matter.

1. ## My aim in this experiment is to investigate how the compression of a spring affects the amount of kinetic energy transferred to the trolley that it is attached to.

Apparatus I will be using the following equipment in my investigation: * Trolley (with spring attached) * Ruler * Cardboard * Light Gate (connected to a computer) * Smooth surface * Calculator Method The trolley will be adjacent to a wall, allowing the spring to compress against it. The light gate, position with a clamp, will be fixed directly above the trolley slightly away from the wall. There will be an upright strip of cardboard attached to the near front of the trolley which will pass through the light gate after the compression of the spring.

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2. ## Physics Investigation on Hook's Law.

At that point the spring will have reached the point where Hooke's law is no longer accurate. I will do enough experiments to find and exceed the elastic limit. I predict I will need to take about 12 measurements. I will record the spring's extension in mm. I predict the spring's extension will increase in about 40mm each time, until the spring reaches its elastic limit. My predictions are based on Hooke's Law, which basically says if you stretch something with a steadily increasing force, then the length will increase steadily too. I predict the results I gather are going to be reasonably reliable and accurate, also very close to the line of best fit.

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3. ## Silent Spring presentation.

Setting the stage for the environmental protection movement. In addition, Carson disproves her former belief that nature was too great and powerful a thing to ever be effected by humans and their actions. About the author Rachel Carson was born on a farm in Pennsylvania in 1907. She graduated from Pennsylvania College for Women in 1928 and went on to study a Masters in Marine Biology at John Hopkin's University in Baltimore. She continued her academic career teaching at the University of Maryland before finding employment at the US Fish and Wildlife Service.

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4. ## Investigate the effects of how springs and elastic bands stretch when weights are hung on them and how springs and elastic bands stretch when the weights are unloaded.

I also predict the more the weight the further the elastic band will go from its starting point. Apparatus: The equipment that I used for this experiment was: * Griffin 100g weights x4 * 1 metre ruler x1 * springs x2 * Clamp stand : * Boss x1 * Clamp x1 Explanation of Hysteresis: Hysteresis represents the history dependence on physical systems. If you push on something, it will yield: when you release, does it spring back completely? If it doesn't, it is showing hysteresis.

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5. ## Investigation of the structure of a cantilever beam.

The weights will be added from 100g till it becomes 1 kg, and every time we add 100g we must measure the deflection of the ruler. This can be done by measuring the initial position of the ruler and measure the deflection from the initial position to the bent position of the ruler with a ruler, to give the bent or deflected height of the ruler. As the weights are added to the ruler the side of the ruler where the weights are hung is under tension and the other side is in compression.

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6. ## For this investigation I have been asked to find out how different masses on a spring effect the extension when the springs are in parallel, series and on a single spring.

If two springs are placed in series, I believe that the extension of the springs will be double the extension of a single spring with the same load (therefore will have half the spring constant of a single spring); and similarly if two springs are placed in parallel then the load will be spread evenly across the two springs so it will require twice the load to produce the same extension of only one spring (and have twice the spring constant of a single spring).

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7. ## "Bridging the Miles Between East and West" - compare and contrast.

The climates of the two cities represent their greatest diversity. Maryland is a Mid-Atlantic state on the east coast where the weather is, as one would expect, cold in the winter and hot in the summer. It may snow in the winter, but not very often and not very deep. Summers are hot with humidity reaching 90% at times, creating a muggy atmosphere. It is in the spring and fall, however, that Maryland is at its best. In March, balmy weather starts rolling in, enticing tulips and crocuses out of their cold beds.

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8. ## Stretching Springs/Hookes Law.

This graph shows the increase in length of an elastic wire as the stretching force on it increases. Over the straight-line part of the graph there is a 10-mm increase in length for every extra Newton (N) of applied force. The change in length (strain) is proportional to the force (stress), a relationship called Hooke's law. The wire begins to stretch disproportionately beyond an applied force of 8 N, which is the wire's elastic limit. When this force is removed, although the wire will decrease in length somewhat, it will not go back to its original length. What happens to a spring when forces are added to it?

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9. ## Investigation based on Hooke's law.

Elasticity can also be shown in this simple diagram: The Molecular Level Description. Before. After. Combinations of springs. Hypothesis. 1) I think that the stretch of the two springs in series will be double the stretch of a single spring. 2) I think that the stretch of the two springs in parallel will be half the stretch of a single spring. Therefore if x were to be the single spring: 1) The springs in parallel would be 1/2 x 2)

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10. ## What is the spring constant?

After each weight has been added to the spring, a pencil mark will be made on the label. When the 12th weight has been added and the pencil mark made, the weights will be removed and placed in the order in which they were added. The label will now be removed and the compression measured and recorded to the nearest half millimetre. A new one will be put on and the process repeated twice so three sets of results are obtained. To try and reduce the error in the measurements, 3 sets of readings are taken, and the average taken.

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11. ## Find out about the energy changes in a tethered cart.

Therefore I will not change the angle of elevation of the ramp from the bench (which includes the height the end of the ramp is from the bench), the same spring and cart will be used throughout the experiment and the string will be tied on to the clamp, spring and cart with no adjustments for the whole experiment. After watching a preliminary experiment I decided on the ranges of distances that I would pull back the cart. I am going to take seven different values for this because having more points on graph makes it more valid as the best-fit line can have a more definite position.

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12. ## Forces, waves and radiation.

I shall then be suspending the spring from a clamp and stand. I shall then place my weights on the lower end of the spring. I shall start the experiment by measuring how long the spring is at the starting point which enables me to take the other results accurately. After that task has been completed I shall be suspending a 50g weight from the spring. This will hopefully stretch the spring slightly. I will then measure the length of the spring and take away the starting point measurement, which will then give me an accurate reading of how far the spring has stretched.

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13. ## How is the sag of a bridge affected by the load applied at it's mid-point?

I will now find out the best width to use by putting two or more rulers side by side. Width (no. Of rulers) Sag (mm) 3 10 2 60 1 150 This graph shows me that using one ruler thickness will give me the best results. I can now decide on the thickness of the ruler to use by putting two or more rulers on top of each other to get different thicknesses: Thickness Sag (mm) 1 150 2 90 3 50 From this graph I can see that I need to use only one ruler to get the best results.

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14. ## Investigation to find out whether or not it is correct to call a rubber band elastic.

This gives me 2.2, 2.0 and 2.5 as 2 is the average round number I will use this. To make the experiment a fair test I will do the experiment three times to gain a fair average. Each of these times I will also use the same type of rubber band as a different type of rubber could effect how far the band will stretch and therefore my results. I will also try to add the weights gently so that the force of it being applied to the band does not affect my results.

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15. ## Physics - The aim of this practical investigation was to obtain a value for the spring constant k for a decided system of springs.

Diagram for Hooke's Law experiment Method Set up the apparatus as shown above, I will be using three springs in series in my experiment. Ensure that the ruler is vertical, making sure not to knock or move the apparatus at all after it has been set up. For safety place a large mass on the clamp stand to prevent it from falling over. Various other safety considerations must be taken such as limiting the size of masses used, wearing safety goggles in case of flying springs and keeping feet well away from possible falling masses.

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16. ## Investigation to show how Elastic Bands Behave Under Load.

The elastic band will regain its initial shape and it behaves elastically. The thinner band will also have a longer extension because the molecules are less intertwined and so the band isn't as strong, when weight is applied the band will stretch further than a thicker rubber. In the thicker rubber band the molecules are more intertwined therefore the band will become stronger so the band will not stretch as far. In the shorter rubber band the molecules are much smaller and are more intertwined, this causes the band not to stretch, as far so it will have a smaller extension.

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17. ## In Ozymandias and Spring and Fall how do Shelley and Hopkins explore the passage of Time?

He is appealing to the reader's imagination of what could have been by describing the fallen kingdom that is. He is looking back on time that has passed. In contrast, in Spring and Fall, Hopkins is talking of time that is currently passing, rather than looking back on time that has gone already. Unlike Shelley, Hopkins is talking to a certain person, rather than just any audience who happens to be reading the poem. Spring and Fall is a very personal account of the passage of time, and though less foreign, it is also less familiar in the reader's mind.

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18. ## The aim of this investigation is to examine the effect on the spring constant placing 2 identical springs in parallel and series combination has and how the resultant spring constants of the parallel and series spring sets compare.

As the magnitude of extension of the string approaches this elastic limit, the extension will gradually cease to obey Hooke's law. At this elastic limit, several changes in the composition of the spring can be observed. Whereas any stretching of a material that occurs below up until this limit is referred to as elastic deformation, stretching the material beyond this limit will result in permanent deformation of the material. Stretching that occurs beyond the elastic limit is referred to as plastic deformation.

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19. ## The 'perfect storm' that formed off New York and the hurricane-like storm during the Sydney to Hobart yacht race in 1998 had many similarities and differences in the way that they formed and how the people involved with them reacted.

Also the shallow water in the bass straight caused steep and savage waves. The intensity of both storms were similar also, in the case of the Australian storm reports from satellite images and competitors revealing average winds of 120 kph, with the strongest being 171 kph. The average wave height was recorded as 12 metres, but the biggest was 20m, however rogue waves were considerably bigger being recorded to be over 25 meters high. The 'perfect storm's' intensity was only slightly different with rogue waves being more powerful, up to 30 meters high yet wind speeds less than the Bass Straits, around 141 kph.

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20. ## What is the speed of sound waves?

Also you can see how the line goes through the origin, which should be so. This line of best fit allowed me to calculate the speed of the sound waves in the air. This is because the gradient of this line equals the speed. The gradient for a straight line is found by dividing the change in Y by the change in X. Gradient = Change in Y Change in X However, in this case the gradient will be the speed.

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21. ## The aim of the experiment is to determine which factors affect the oscillation of a pendulum.

The amplitude of an oscillation is the maximum displacement of the system from its rest position. There are a number of other oscillations. Mechanical oscillations, for example, are in use everyday. The suspension units on cars and motorcycles are oscillators. They are, however, designed to provide smaller amplitudes as the oscillations continue: they dampen down. A car will bounce up and down only a few times before coming to rest. Once started, oscillations gradually die away. The kinetic energy of the oscillation is transferred to heat through fiction, so that the amplitude gets smaller and smaller.

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22. ## My aim is to investigate what factors affect the period of a Baby Bouncer. The factor that I will be varying will be the mass on the end of the spring.

I am using this prediction due to what is stated in Hooke's law. Equipment Used * Spring * Clamp Stand * Stopwatch * Weights * Ruler Method * Equipment will be set up as in diagram above. * The weights will be dropped from the top of the spring. The stopwatch will be started when the weights are dropped. * We will count 5 oscillations. When the fifth oscillation has been recorded, the stopwatch will be stopped. * This will be repeated 5 times for each mass, and we will be using weights from 100grams to 1000grams, increasing each time by 100grams.

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23. ## My aim in this experiment is to find out how force affects the extension of a spring.

Weak springs are very sensitive and can be used for measuring small forces. Strong springs can withstand larger forces. Preliminary To help me come up with an initial theory I will carry out a preliminary experiment. For my preliminary I will investigate how mass affects the extension of a spring. The apparatus I will use is a 25mm spring, a clamp to hold the spring, 100g masses and a ruler to measure the length of the spring. The variable I will change is the mass. All the other apparatus remained constant. My method is to connect the spring to the clamp, attach the mass to the bottom of the spring and measure it by holding a ruler to the side of it.

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24. ## Experiment on Hookes law using bridges

So we are looking for 10 results and that should enough to draw a suitable graph. We shall then be able to measure the sag, which is caused by the mass on the main beam using a ruler; we shall measure the sag from its lowest point to the floor (fig.3). We shall repeat the experiment for the same weight times so we have an accurate reading, if the measurements are not all the same then we shall take the resulting average.

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25. ## I am doing an investigation in to how much a metre rule bends when one end is clamped to a table and a varied load is attached to the other end that hangs off the table, thus bending the rule.

If the rule did snap, we could say that it had gone passed the elastic limit, which means that if something is bent beyond this point, in the case of the metre rule, it would snap and not be able to return to its original shape. Hooke's law can only be applied up to the limit of proportionality as after this, permanent damage is done to the metre rule. It no longer obeys Hooke's Law as equal increases in stretching force produce larger increases in extension than expected.

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