Of The Elastic Potential Energy example essay topic

Aim: To investigate the pattern in the amount by which a hanging piece of elastic stretches when a load force is applied and the amount by which the stretch is reduced when the load is removed. Aim (in simpler terms): To determine the relationship between the force on a rubber band and its stretch, both during extension and retraction. Hypothesis: Not required. Method 1) Hang a piece of elastic on a clamp stand. Ensure the elastic is new. 2) Clamp a ruler using the clamp stand.

Ensuring the markings on the ruler is as close to the elastic as possible. - Draw a diagram 3) Measure the length of the elastic and record the data. 4) Hang masses on the elastic until it reaches it point of irreversible distortion. Take note of this weight; do not hang more than this weight in the experiment. 5) Add a weight of 100 N (change appropriately). Wait for a few seconds for the system to "stabilize".

Measure the length of the elastic and record the data. Special care must be taken to ensure that when the mass is added the elastic should not retract. 6) Add more weights, till the total weight is close to its point of irreversible distortion or till there are no more weights. 7) Remove the weights one by one. Wait a couple of seconds for the system to "stabilize". Ensure that when the mass is removed the elastic should not be allowed to stretch further.

8) Repeat, till there is no more mass on the elastic. Measure the length of the elastic. Equipment Elastic Clamp stand Ruler Different weights or a weight hangerVariablesIndependent: Mass hung on elastic Dependant: Length that the elastic extends or retracts. Controlled: Same conditions - thus the behaviour of the elastic is constant Same equipment Results Force (N) Length of elastic (m) Length that elastic was stretched During extension During retraction For extension For retraction 0 1 1.2 0 0.2100 1.5 1.4 0.5 0.4... 900... 1000...

Note: To find the length that the elastic was stretched. Simple subtract the value "During extension" by the original length of elastic. Then write the result in the column "For extension" for the appropriate weight. Repeat for retraction. Construct a graph of this data. For ease of data interpretation, graph force on y axis and length that elastic was stretched (that is the column "For extension" and "For retraction) on x axis.

Also possible to have intervals of 0.98 N on y axis so that value of mass in grams can be plotted accurately (assuming g = 9.8 m /'s ^2) Plot the points and draw a smooth curve. Draw a smooth curve through the points "For extension" and another smooth curve through the points "For Retraction". Indicate which curve is which. (colour code and / or label) A possible idea for further processing of results is to calculate the amount of work done. That is the area under the graph. An example of what your graph should look like: The graph may be shaded to help further understanding of the meaning of the graph. As shown in graph below: The total shaded area (green + blue) shows the total work done on the rubber band.

W = F. the green area represents the work done by the rubber band. That is the energy that is restored. The green area is clearly less than the total area (green + blue). This shows that there is a loss in energy. The blue area represents the energy lost. Conclusion (well, what you should have concluded): The graph shows a hysteresis loop, the relationship between the two variables depends not only on the independent variable but also on whether the independent variable is increasing or decreasing.

The area in between the extension and retraction line shows the energy lost. Thus, we may infer that the elastic is a non conservative force because the energy put into the system is not equal to the energy that is given out by the system. The force applied on the elastic is not recoverable. Discussion Scientific idea An ideal spring that obeys Hooke's Law will extend and retract by the same amount. This implies that the work done to the spring is equal to the work done by the spring. Consider then a spring made of very ductile material.

When stretched there will be no restoring force. That is even after the weight is removed, it will not retract at all. The ideal spring and the spring of very ductile material represent the extremes of elastic behaviour. The elastic we used however appears somewhere in between. For when work is done on the elastic, the elastic does some work too. However, the work done by the spring is slightly less than the work done on it.

The relationship between the force applied and the extensions is hysteresis. (Hysteresis is the dependence of the system on its previous state, generally in the form of a lagging of a physical effect behind its cause.) This relationship is caused because the work done onto the elastic is not equal the work done by the elastic. There are many reasons for this. One of the observations during our experiment is that when the elastic was stretched a small amount of heat was given out. If we then carefully consider the nature of elastic we can conclude two things: a) since our elastic is a polymer. It is composed of thousand of molecules that are strung together with some cross links.

When the elastic is stretched, we end up breaking some of the bonds between the molecules. Also, since heat is given off, we could proceed to say this is an exothermic process. To prove this, we could gently heat our rubber band after it has been used for the experiment to return it closer to its original length. This is in accordance with Le Chatelier's Principle. However, it is important to note that not all the energy will be restored by heating it thus the bonds that have been broken when the elastic was stretched may not be repaired, so we must not expect the elastic to return to its original state. We can expect it to get closer to its original length. b) When the elastic was in its relaxed state, the molecules in the elastic were disorder.

This implies high entropy. When we stretch our elastic, the molecules become more aligned. This implies lower entropy. Furthermore, since heat energy was given off this confirms that the entropy of the system has decreased. Thus, when the elastic was retracting, it returns to its disordered state. The process is not reversible, therefore the entropy in the system has increased (the entropy of the Universe increases in all real processed).

This would account for the lost in energy when the elastic was extended and retracted. - The lost of energy is due to fibres in elastic being broken and given out as heat. Evaluation Method The ruler supplied did not look straight, it seemed so slightly bent. Therefore our results are probably slightly biased.

Parallax error was reduced by having the markings on the ruler as close as possible to the elastic when the elastic was being measured. Also when reading the measurement, the eye was parallel to the markings on the ruler. Meaning our results are more precise. Implying higher level of reliability.

Several trials were done. The average of the trials was calculated and graph. This meant that the values used to construct the graph, had less random errors and was more precise. This increased the reliability of our results. It was very difficult to reduce vibrations when the experiment was being done.

Perhaps this experiment should be repeated in a less crowded environment with more space. The reduction of vibration is important, for due to this vibration, more friction could be released thus increasing the level of entropy and making the system lose more energy. Also, if the amplitude and frequency of the vibration was accurate. It could have decreased friction by helping the molecules slide pass each other. This would then decrease the energy that is lost. Either way, vibration is not desirable in this experiment.

The elastic was not allowed to retract when more mass was added. This was so that the fibres in the elastic would not be damaged as much. Furthermore, by letting it retract, some of the elastic potential energy stored would be released. Thus affecting our results. Similarly, the elastic was not allowed to stretch further when the mass was being removed for the same reason. Improvements Repeat experiment with the same elastic, to see the behaviour of the elastic after repeated stretches.

Do the experiment in different conditions, mainly with a higher temperature. Since when the elastic is stretched heat is given off. Perhaps, if the room temperature is sufficiently high enough, the rubber band will not give out heat, it will be absorbing heat. Since the elastic does not give off heat, then less energy will be lost.

So this would mean that the elastic will be a more ideal spring. As usual always ask for better equipment. Resources web.