Title:

Investigate the Strength of Straw.

Purpose / Aim:

To Investigate the Relationship between the Number of Straw Used and the Strength of Straw when Weigh is Constant.

Abstract:

        The purpose of this experiment is to investigate the relationship between the number of straw used and the strength of straw when weigh is constant. First and foremost, 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.

        Based to the theory, 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.

What we realized after conducting this experiment is 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.

Research Question:

• What is the relationship between the number of straw used and the strength of straw when weigh is constant?

Hypothesis:

        In this experiment we are going to investigate the strength of straw that is represented by the reading of meter ruler and the number of straw used. We predict that when the number of straw increases as the result the length of stretched straw will decreases due to constant weigh. We also predict that when the length of stretched straw decreases; the strength of straw will increase. Also, in other word we can say that the number of straw used is proportional to the strength of straw when weigh is constant.

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)

No. of Straw

Calculation / cm

1

= 40.1 – 36.0

= 4.1 cm

2

= 40.1 - 36.5

= 3.6 cm

3

= 40.1 – 37.3

= 2.8 cm

4

= 40.1 – 38.3

= 1.8 cm

5

= 40.1 – 38.8

= 1.3 cm

• Second Trial:

• Third Trial:

Calculation for the Uncertainties:

In order to calculate the uncertainties and error for the above calculation, we can use this equation:

• First Trial:

• Second Trial:

2. Besides that, in order to get an accurate result we should use the laboratory apparatus which in the best condition.

3. 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.

4. We also need to be more careful and cautious in running this experiment.

Conclusion:

1. Hypothesis is valid and accepted.

2. 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:

1. In the early discussion, I contributed some notion about how we will conduct this experiment, the aim of this experiment and so forth.

2. 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.

3. 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.

4. 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.

5. I conducted this experiment with helping from my partner till the end.