a α b, where:
a = Number of straw used
b = The strength of straw
Actually we decide our hypothesis based to the theory below; “While for the straw itself, when we stretched it, we are trying to overcome the intermolecular bonds between the molecules. At the same time we are also trying to change the position of molecules that are held together by the intermolecular bonds. With vary number of straws; its strength also will increase”.
Theory:
Term such as strength, stiffness and toughness are used in a special way by physicists. Strength refers to the quality or state of being strong, in particular the capacity of an object or substance to withstand great force or pressure. While stiff or stiffness means small strains for large stresses (large Young modulus); not stretchy or bendy. Tough or toughness means undergoes considerable plastic deformation before it breaks. Consequently, tough materials absorb a great deal of energy before they break.
In the experiment, when choosing a material it is always important to consider how the material behave under the conditions in which it will be used. For example, concrete is very strong under compression, but is weak in tension, where it breaks by brittle fracture as cracks open up. Aluminum has a similar stiffness to glass, but glass is usually brittle and shatters for very small strains whereas aluminum undergoes plastic deformation before breaking. In other word it is tough. While for the straw itself, when we stretched it, we are trying to overcome the intermolecular bonds between the molecules. At the same time we are also trying to change the position of molecules that are held together by the intermolecular bonds. With vary number of straws; its strength also will increase.
Apparatus:
Straws, retort stands, slotted mass carriers, slotted masses and meter ruler.
Variables:
- Independent Variable : The number of straw
- Dependent Variable : The length of stretched straw (strength of straw)
- Constant Variable : The number of slotted masses (weight = 1000g)
Diagram:
Procedure/ Method:
- The apparatus was set up exactly like shown in the diagram above.
- Experiment was started by using one straw. The initial reading from the pointer was taken before the masses were suspended.
- Then, the slotted mass carrier together with constant masses in detail, 1000g, was suspended at the straw.
- As the result, the pointer will give the new reading. That reading was taken as the final reading
- Step 2-5 was repeated for vary number of straws.
- All readings those taken were recorded and tabulated.
Table of Values:
Analysis of Data:
Calculation for the Length of Stretched Straw:
Calculation for the Uncertainties:
In order to calculate the uncertainties and error for the above calculation, we can use this equation:
Thus based to all table above, the length of stretched straw:
-
Comparison Graph About the Length of Stretched Straw In First, Second and Third Trial
Evaluation / Discussion:
After carried out this experiment, we realized that our prediction is correct. Once the number of straw increases as the result the length of stretched straw will decrease due to the constant weigh. While, when the length of stretched straw decreases; the strength of straw will increase. This is mean; the number of straw used is proportional to the strength of straw when weigh is constant. Or, in equation form;
a α b, where:
a = Number of straw used
b = The strength of straw
According to the result, what we can say is there are some weaknesses in running the experiment. Obviously, this thing we can see in the second trial. More specifically for the 2 straws and 3 straws. There is just little difference between the lengths. This thing can’t happen because logically when the number of straw increase as the result the length of straw should be drastically increase too.
All these weaknesses occurred due to some reasons:
- This thing might happen in virtue of our mistake while taking the readings from meter ruler. We should be careful because the parallax error and zero error might occur while taking the reading.
- Besides that, the effects of a change in surroundings might also affect the result of this experiment. It might in the form of sunlight, wave, water moisture and so forth.
- Apart from that, many laboratory apparatus that we used is in dissatisfied condition and already outdated. For example, we realized that the scale meter ruler is not accurate or precise than it supposed to be.
- The observer being less than perfect in the same way every measurement.
There are several ways to overcome these problems from occurred again. We can prevent it by making some improvements:
- First and foremost, try to avoid mistake while taking the readings from the measurement device. We should realize that parallax and zero error can occur while taking the measurement of the length of stretched straw.
- Besides that, in order to get an accurate result we should use the laboratory apparatus which in the best condition.
- We also can repeat this experiment may be for 3 or 5 times in order to obtain an accurate result. This is because we can avoid random errors.
- We also need to be more careful and cautious in running this experiment.
Conclusion:
- Hypothesis is valid and accepted.
- After running this experiment, we realized that once the number of straw increases as the result the length of stretched straw will decrease due to the constant weigh. While, when the length of stretched straw decreases; the strength of straw will increase. This is mean; the number of straw used is proportional to the strength of straw when weigh is constant. Or, in equation form;
a α b, where:
a = Number of straw used
b = The strength of straw
Contribution:
- In the early discussion, I contributed some notion about how we will conduct this experiment, the aim of this experiment and so forth.
- I tried to find the method that we were going to use in order to carry out this experiment from the reference books in library. I also make further read about this topic.
- I explore the Internet to find the website that related to this experiment. I found many websites that can help me in running this experiment.
- I briefing my partner about the method that suggested by me because at the beginning of experiment, we keep argued with the method that we were going to use.
- I conducted this experiment with helping from my partner till the end.
______________________________________________________Mohd Hafiz Bin Mohd
-