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AS and A Level: Waves & Cosmology
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- 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 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 Blueshift can be observed from ‘nearby’ stars and galaxies.
- 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 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 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 The uncertainty over the value of The Hubble constant is becoming smaller as measurements of distance to galaxies improve
- 5 Since redshift is seen in every direction, the conclusion is that the universe is expanding.
Fate of the universe
- 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 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 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 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.
Firstly I will make sure that an equal amount of mass (100g each time) is added each time. Then I will make sure that the readings are taken accurately, by using a splint to measure and mark the exact millimetre on the ruler. I will also make sure the spring is as close to the ruler as possible and also hanging off the table if the weights exceed past it to, make sure I get an accurate reading. As if it leans on the desk it could effect the extension and the deformation of the spring.
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How may the study of earthquake waves be used to interpret the earth's internal structure and composition
Earthquake foci are located at depths under the surface up to a maximum of approximately 700km. They are grouped into shallow (0-70km), Intermediate (70-300km) and Deep (300-700km). The zone in which earthquake foci are found is called the Benioff zone. The focus of any earthquake cannot be found any deeper than about 700km, this suggests that the composition of the earth below this depth is different from above it and so is not adequate for earthquake foci to be located and therefore it must change from a rock that can be easily fractured to a less easily fracturable rock.
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The accuracy in this investigation is due to testing the results twice because we did this we need to add a average column and a average column means a extension column. Key: Force(N)= how much newton's are applied to the rubber band. 1 +2 = These are the number of times I tested the rubber band/plastic bag/ spring. Average = The numbers in columns named 1 +2 are added together then divide the answer by 2. Extension = The numbers in the average column take away from the top number in the Average column.
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As you can imagine a field of dynamos all going as fast as they can would be very noisy. As we all know wind is a renewable source of power and because it doesn't burn fuels it is environmentally friendly. Waves possess great energy. Experiments with various different designs of generator have proved that waves can provide electricity. However, there are problems in developing and building wave powered generators which are both cheap and efficient, as they must be strong enough to cope with storms while being light enough to work with small waves.
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10 weights (each 1N each) Safety: There are very few potential dangers whilst performing this investigation. The spring could snap and the stand could fall. To prevent these factors from dangers I shall wear goggles and make sure the stand is supported on both sides. Fair test: To make sure that I will get the most accurate results possible I will have to make this a fair test. Things that I shall carry out to make it fair it to keep the 1 metre rule in the same position.
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I also counted 10 complete bounces of the spring and divided it by 10 so that the time of one bounce would be more precise. I made sure that I started the stop clock as accurately as I could so that my three individual tests would be very similar and this was shown in my results. The variable I am using is the amount of springs used and in what order, this is the only thing I am changing so that my test is fair.
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Variables There are many things I could change to alter the outcome of my experiment. A list of variables I could change which may affect the results of my experiment are; � Length of the elastic band, � Width of the band, � Elasticity of band, � Previous stress and strain the band has undergone, � Weight of band, * Weight added to band, � Colour of band, � Temperature of band and room at time of experiment. I have deemed these last two factors insignificant as I feel they will not have an actual effect on the outcome of my experiment.
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We did a similar experiment with springs instead of an elastic band. The more weight added the longer the spring extended. I have also taken into account Hooke's law. Hooke's law simply states that the extension of a spring (Or other stretch object) is directly proportional to the force acting on it. This law is only true if the elastic limit of the object has not yet been reached. Plan First I will attach an elastic band to a clamp-stand and will suspend the elastic band over the end of a table.
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(-Robert Hooke (1635-1703), English scientist, best known for his study of elasticity. Hooke also made original contributions to many other fields of science.) He said that extension is proportional to the downward force acting on the band, and there will be a elastic limit where the band and the spring can't take no more and will constantly drop and with the band it will actually break. PILOT TEST: Before the actual investigation we did a pilot test to see our estimate results. 'Apparatus: stand & clamp Newton meter Spring elastic band 'Method: In the pilot test I used the above apparatus.
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Where : T = Periodic Time (s) K = Spring stiffness G = Acceleration due to gravity (m/s) This means that K is the spring stiffness (or spring constant), F is the weight or force applied to the spring and X is the extension of the spring after the force has been applied. Graphically: B Extension (x) A Load (F) This is the graph that I expect to find from my results as it means that the extension of the spring will increase proportionally to the force that is applied to it. The graph should also curve at the top as this will be the elastic limit and will be unable to return to its original position and shape.
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by doing the following: F = ke Rearrange formula to get k F/e = k I know that F = mg and e in this case is 0.085 m is 0.05kg and g is taken as 9.81ms-2 Therefore, F = 0.05 x 9.81 F = 0.4905N Having found F I can use this to work out k: k = F/e k = 0.4905 / 0.085 k = 5.77 (3sf) The spring constant in this case is 5.77. Using k I could predict the extension of this spring if the weight suspended from it was known or the weight suspended from it if the extension was known.
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Prediction Based on my scientific knowledge of Hookes law (extension is directly proportional to the stretching force) and my oscillation of a pendulum experiment which proved Hookes law I predict that the weight I put on the bottom of the spring will be directly proportional to the time taken for one oscillation. Therefore, when I double the weight on the bottom, I will be doubling the time taken for the spring to oscillate. However, based on class discussion and my previous experiment I also predict this rule will not apply after the spring has passed its elastic limits (approx.
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To investigate the relationship between the extension of a compact steel spring and the force producing that extension and to determine the elastic limit and force constant of the spring
After the elastic limit has been reached, the spring stops obeying Hooke's law. Point A is an example of where the mass is removed and the extension remains. This is called the yield point. The extension that remains is the measurement OS that is recorded at the base of the graph. The force constant of a spring is the force needed to cause unit extension. If force (F) produces extension (e) then this can be shown as: Hypothesis From the theory I expect to find that I will get a constant extension with every 100g added to the spring.
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apart so less extension. Less force acts on each molecule. In series 1 spring In parallel '2 springs' If there are double the amount of springs in parallel then I predict that the extension will be half. I predict that the extension is inversely proportional to the number of springs. If I applied 2N to one spring and the extension was 5cm then if I added on another spring (in parallel), I would say the extension of the springs would be 2.5cm.
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Hook the 20swg spring onto the clamp stand. . Move the metre stick to line up an easy figure with the bottom of the spring e.g., 200mm to make the results easier to record. . Add a 10g mass and record the extension each time until the spring won't return to its normal position. . Do the above for each spring making sure you record it to the nearest millimetre. Measurements I will be using, 10g masses to extend the springs, a 1metre stick to record the extension, and 5 nichrome springs with a gauge of 20swg, 24swg, 28swg, 32swg, and 36swg to extend.
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The springs would extend to compensate the allowing of the energy release. Testing these factors, I will also investigate certain springs benefits over another type of spring. HYPOTHESIS I believe that out of three types of materials being tested in this experiment [wires/springs/elastic bands], the spring will perform the best in the testing if the material will go back to its original shape. I also believe that the less taut the spring is under, the better the spring acts under the pressure of compression and extension.
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The more molecules there are the more energy is needed to weaken the bonds. When a load is applied this creates gravitational potential energy(g.p.e). Therefore, materials smaller in width and length need less weight for the elastic limit to be reached. VARIABLES There are several variables which when altered will effect the behaviour of elastic bands and springs. To make a fair procedure their are certain variables that need to be controlled, and others that need to be varied in order conduct the experiment and give a detailed conclusion. The room temperature will effect the experiment, if it drops the particles will vibrate less, and will be drawn closer to each other, meaning the bonds will be harder to break and the material will contract.
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'I predict that the extension will double if the force doubles and the extension will treble if the force trebles. I also predict that the rubber band will not return to its normal length once it has reached its elastic limit as it will be plastic, and I support my prediction with Hook's Law. To make this a fair test I will add and remove the same weight each time. To make my measurements as accurate as possible I will take the reading by placing a mirror behind the meter ruler and placing the pin through the bottom of the rubber band.
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These values will allow us to plot a graph from which we can clearly analyse the results. The results will be measured in the following table: Distance (in cm) Voltmeter reading (in volts) Voltmeter reading 2 (in volts) Voltmeter reading 3 (in volts) Average reading (in volts) 0 10 20 30 40 50 60 70 80 90 100 Background light will also be measured and taken into account as the experiment is conducted. Background light is light from sources other than our own; these include other experiments being conducted, and natural daylight, which could interfere with our results.
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The most important thing in this experiment is not the total length but the extension. If the spring is stretched a bit to far it will behave inelastically and it won't follow Hook's law and it won't go back to its original shape. When drawing the graph and the results are in a straight line up to one point and then start to curve this is inelastic behaviour.
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This way the spring is still and it will stay in the same position for every weight. Diagram Method * Set up all the equipment as shown in the diagram * Add chosen weights to the spring * Record you results I will need to take the readings for loading and unloading of the weights because then I can see the extension of the spring. I will check that I have not exceeded the elastic limit by measuring the spring before I put on a different weight to see if the length has got longer.
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Up to this point, a spring can return back to its original shape and size, however beyond this point, the spring will become permanently stretched and deformed. Now I am going to investigate the factors, which affect the extension of an elastic cord, instead of a spring. The factors, which affect the extension of elastic, are; * The amount of force applied * The thickness of the cord * The length of the cord * The width of the cord * The temperature of the cord The elastic cord is made of rubber, rubber is a special type of molecule called polymer.
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no block, and so the lateral displacement grows as well, so that when the dragging away is doubled, so will the lateral displacement. Because of this, I think my results will be directly proportionate. Measurements, Fair Test and How to be accurate The measurements of the block are 2cm x 6 cm x 11 cm, and I will be using two blocks. The blocks will be put together, so that I can get more than three results. The Sizes of the amount of glass that the ray passes through will be 2cm, 4cm, 6cm, 8 cm, 11 cm, 12 cm, 13 cm, 17 cm and 22 cm.
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To Determine the Spring Constant of a Helical Spring and a Value for the Earth's Gravitational Field Strength
* I will set-up an experiment to show the relationship between force and extension so I can calculate K, the spring constant. * My results will be repeated and averages taken, to ensure 'fair' results. * I will also take my results whilst loading and unloading the various weights to ensure the spring has not extended past its elastic limit. APPARATUS: * Clamp and stand * Metre Rule * Spring * Weights (10 x 10g, 8 x 100g) * Scales (accurate to +0.01g)
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The gradient will in turn the Young's modulus. The initial gradient in the elastic gradient will be calculated to find the Young's modulus. As mentioned, I will compare the difference in Young's Modulus between a pure metal (copper) and one of its alloys (Constantan). I will find the difference in stiffness and consider whether it affects any other physical properties such as tensile strength and ductility. The data book suggests that the Young's modulus of Copper and Constantan are 12*1010 Pascal and 11*1010 Pascal respectively.
- Word count: 1758