In this experiment, I am going to find out the relationship between Force and extension using stretchy sweets and then find the stiffness of stretchy sweets using Hookes Law.

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STRETCHY SWEETS EXPERIMENT

In this experiment, I am going to find out the relationship between Force and extension using stretchy sweets and then find the stiffness of stretchy sweets using Hookes Law.

Hookes Law states that extension in a material is proportional to the force applied provided the proportional limit is not exceeded.

To do this, I will use a fixed length of stretchy sweets and suspend different mass of metals on it. Then I will find the extension on the sweet for each suspended metal of known mass. I will carry out first a trial experiment to find out the behaviour of this sweet under different load and to see if it returns to its original length after unloading it.

There are several factors that may affect the extension of the stretchy sweet. Some of them are:

* The material of the stretchy sweet

* The cross sectional area of the sweet

* The length of the stretchy sweet

* The temperature in the lab

In doing this, I have to keep the material of the sweet constant by using the same type of sweet each time. The cross sectional area of the stretchy sweets will be kept constant by using stretchy sweets with the same diameter. The temperature will be kept constant by performing the experiment in the lab at room temperature, because an increase or decrease in temperature will cause the stretchy sweet to either expand or contract thereby affecting the extension of the sweet when a load is applied to it. For a fair test, I will use the same length of stretchy sweets each time I repeat the experiment and I will also ensure that the length of stretchy sweet that I use is long enough, because longer sweets gives larger and more measurable extensions.

PREDICTION

I think that as the load applied to the stretchy sweet is increased, so will the extension and the rate at which it increases will be proportional to the applied load (i.e. F?e) provided the elastic limit is not exceeded.

This is because of the structure and arrangement of molecules in the stretchy sweet. When a load is applied to the sweet the molecules in the sweet straighten out as atoms in the lattice slide over each other, allowing the sweet to become longer. Increasing the applied load will cause a deformation in the arrangement of molecules and so the sweet will break. But as long as there is no deformation in the structure of the sweet, the molecules will then regain their original positions when the load is removed.

By plotting my graph of extension against force/load, it will reveal a region where extension is directly proportional to the force. Then I will find the stiffness of my sweets using the formula F=kx, where F is the force measured in Newton's, x is the extension measured in metres and the constant k is the stiffness measured in Nm-1.
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TRIAL

APPARATUS

. Stretchy sweet over 0.50m long

2. Stop clock

3. Clamp stand and a block of polystyrene

4. Set squares

5. A metre rule

6. Micrometer screw gauge

7. Cello tape and Plastacine

8. A weighing balance

9. 10grams X 10 of metals

I will set up my apparatus as shown in the diagram and then record the initial length of the stretchy sweet. Using a cork with a pin attached to it, I will suspend the following objects of mass 20.2g, 25.0g, 30.0g, 40.0g ...

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