A simple pendulum consists of a piece of thread which is fixed at one end and has a small metal ball called the bob on the other end. The periodic time T of the pendulum is the time for one complete swing or oscillation. The length L of the pendulum is the distance from the point of support and the centre of gravity of the bob. The amplitude (angular) of a swing is the angle between the extreme and rest positions of the thread. Experiments show that if the amplitude does not exceed 10 or 50, T depends on L and is unaffected by the mass of the bob and the amplitude. The connection between T and L can be found in this experiment. Physics for today and tomorrow, Tom Duncan 2nd by equation, the period T of a simple pendulum is given by T=2π√L/G.
The pendulum is able to work when the bob is raised to an angle larger than the point at which is vertically suspended at rest. By raising the bob the pendulum gains gravitational potential energy, as in being raised, it is held above this point of natural suspension and therefore is acting against the natural gravitational force. Once the bob is released this gravitational force is able to act on it, thus moving it downward towards its original leaving point. The GPE is converted into KE needed for the pendulum to swing once the bob returns to its original point of suspension, the GPE has been converted into KE causing the bob to continue past its pivot point and up to a height equidistance from its pivot point to its starting point. The same factors affect the pendulum on its reverse swing. Due to continuous motion the bob creates an arc shaped swing.
Determination of g using a simple pendulum. A reasonably accurate determination of the acceleration of gravity(g) can be made by measuring the period of oscillation and the length of the pendulum. From the theory of the simple pendulum
T=2π√L/G therefore T= L,π2/G=L
It follows that the gradient of the graph of T squared against L is Lπ2/G, in which case g can be determined by plotting each a graph and measuring a gradient. A graph of T against √L how a gradient of 2π√G and therefore such a graph could have been used to determine g. The reason for choosing to plot T squared against L is that the graph is linear and its gradient is Lπ2√g even if there is an error in the measurement of L providing it is a constant error.
Safety:
Make sure the stool is stable on the table and clamped down tightly for less risk of accidents, and stand away from the pendulum that is swinging which could also lead to accidents.
Results:
Time for 10 swings sec
This chart proves my prediction was correct however my predicted table was quite a way off.
Conclusion:
The graph has a strong positive correlation and has two anomalous results, this graph means the longer the piece of string the longer the time taken for one swing.
Evaluation:
I thought this experiment went very well and the test was as fair as
it could be. The graph and table were very accurate however the
first graph I did in rough took me a long time to do. I improved my
results by making sure I started in the correct place and always stood in front of the pendulum. The method was good as well
much like the enzyme coursework. I knew exactly what I was doing once I was told. The only improvement I would have done to make
the experiment better is not to put the stand and pendulum on a stool as it was very wobbly and not very stable. I do believe this could support a firm conclusion as the information was very well gathered. To make the experiment very stable by using a computer to count the number of swings and see how long it took.
Lewis Wright The Enzyme Investigation 25th July 2001
Aim:
To investigate the effects of varying temperatures on the rate of the protein (Albumin) breaking down by the enzyme (Pepsin).
Introduction:
The measurements were made by using a stop clock to measure the time taken for the pepsin to break down the albumin.
Prediction:
I predict that once the pepsin is added to the albumin at room temperature the reaction will start extremely slowly but as I repeat the process and increase the temperature the reaction will speed up. The reaction will be at its fastest around 30 decrease and 40 decrease but any higher than that and the pepsin will become denatured and the lock and key system won’t work.
Lock and Key System:
Enzyme: Substrate:
A chemical compound The key that
that breaks down food. starts the reaction.
Above 40 decrease C the enzyme usually
becomes denatured.
Fair Test:
To make my experiment fair I will use precautions to make sure that all the liquids used are at the right amount and I will also make sure the temperature of the water baths are at there most accurate. I will also use the same size test tubes and beakers. I will use the same stop clock for each experiment and make my results as accurate as possible.
Equipment:
I have chosen my equipment carefully, I am going to use a thermometer, 6 test tubes, 4 water baths at varying temperatures, a test tube holder, a Bunsen burner, a tripod, a heat proof mat, a gauze, 2 beakers and writing and drawing equipment.
Drawing of Equipment:
Predicted Table:
Method:
Once all apparatus is collected in a test tube add 8ml of water, 5ml of Albumin and one drop of hydrochloric acid, the acid is there so the experiment is as accurate as possible to real life, this is because in our stomach we have a PH of 2 which means we have a small amount of acid in our stomach. To check we had the right PH we used litmus paper and a PH scale. Once we added the right amounts of albumin, pepsin and acid to each test tube we toke the test tubes over to the water bath with the pepsin and the stop clock. Put the test tube into the water bath then when your ready add the pepsin and start the stop clock as soon as all the pepsin is in the test tube, once the mixture has turned colourless stop the
stop clock and record the amount of time taken. You may want to do this a few times with each test tube to get your results as accurate as possible. Do this with the other test tubes at these temperatures, 0*C (put the test tube in a beaker of ice) 20*C, 30*C, 40*C, 50*C, and then 100*C (in a beaker under a Bunsen burner).
Background Knowledge:
“From the books science to sixteen, and living world, written by
Stephen Pople and Micheal Williams.”
Pepsin is found in the stomach of a human body in which our bodies average temperature is 37*C, I predict that the enzyme will work best at 37*C as it is the temperature of the body that the enzyme works best. Also from early preliminary work I found that once the enzyme is healed to over 60*C it will become denatured and die.
Enzymes, what are they?
A substance produced by living organism and acting as a catalyst to promote a specific biochemical reaction, generally enzymes speed up chemical reactions in cells that otherwise would happen to slowly to sustain life. An enzyme itself is not changed by the reaction that it simulates, a catalyst is something that speeds up a reaction.
Results:
temperature
0*C 20*C 30*C 40*C 50*C 60*C
Graph to show amount of time taken for the pepsin to break down at varying temperatures.
These results prove that my prediction was correct and that the reaction happened faster around 40*C.
Conclusion:
In conclusion the graph has a negative correlation. The smallest time taken was 58 seconds at 40*C which means it was the best temperature for the pepsin. The worst time was at 0*C this was the worst times because the reaction was so cold it most probably froze.
Evaluation:
This experiment was rather hard, it was very hard to get the temperatures right in the water bath and to make a fair test was quite a challenge. The results are also very hard to get as you have to start the stop clock as soon as you add the pepsin to the test tube. I made my results as accurate as possible by repeating the process over and over again. The method was very well done and I knew what I had to do as soon as I read the title. The problem with my results are they aren’t as accurate as they could be and can’t hold a firm conclusion.
