Prediction
If the springs follow Hookes law then the graph that should be produced should resemble the graph to the left. Showing that as the load increases the extension will increase proportionally. But this only resembles a single spring on its own. Having springs in parallel or in series will effect the springs constant.
I predict that the springs in parallel will half the spring constant and when the springs are in series the springs constant should double. This is because when the load is kept constant and the extension is decreased then the springs constant is increased. Following this I predict that when the springs are in parallel the resistance to the load will be doubled, therefore halving the extension and increasing the springs constant. Also when the springs are in series the extension will be doubled, this is because the springs resistance to the load will be halved thus decreasing the springs constant.
Apparatus Diagram
- A clamp stand
- Set of 2 springs (20 mm)
- 10 Load weights (100 grams)
- Metre rule (1 mm grading)
- Extra 2 x 1 kg weights
- 2 x 150 mm dowel rods(15 mm diameter)
- Bluetack
Series Parallel
Method
- Set up as Diagram.
- Set springs into a parallel position as shown in the diagram. Using the 2 dowel rod and blue tack to hold the springs in place.
- Attach metre rule to a fixed point so that the readings are taken from the same point each time. Measure from the start of the coils to the end of the coils (shown in diagram). With this note down the original length.
- Add a 100 g weight and measure the new length and note down the measurement in your results table. To work out the extension subtract the original length from the new length.
- Repeat step 4, 9 more times. Each time adding 100 g more. You should then get a range of results from zero grams to 1000 grams. Do not exceed this mass as it may permanently damage the spring.
- Repeat steps 1 through 5 again until you get 3 sets of complete data.
- Repeat the whole experiment (steps 1 - 6) but this time with the springs in series (set up as shown in diagram) and a single spring so comparisons can be made.
Fair test
In order to keep this a fair test I shall : -
- Ensure that the springs used are kept the same in each experiment. Doing so will produce more reliable results.
- I will be using the same weights. Doing so will construct more reliable results, by keeping all the experiments as exact as it predecessor.
- Keep the clamp and stand at the same height from the floor. Doing so will add to the accuracy of my results as an alteration of height could effect the strength of gravity.
Accuracy
To keep my experiment reliable and accurate I shall administer the following procedures: -
- Measuring the new length in millimetres (mm) instead of centimetres (cm), this will make my readings more accurate as I will be taking readings to the nearest millimetre instead to the nearest centimetre.
- Using a metre rule with 1 mm grading is will produce high precision and reliability for this experiment; although a vernier scale would be more suitable and produce more accurate results.
- Loads shall be measured before hand so that an accurate reading can calculated. Not doings could affect my results dramatically.
Variables
These are the measurement that I will be keeping constant: -
- Springs original length (mm)
- Gravity (9.81ms )
These are the measurement that I will be altering: -
- Positioning of the springs (Parallel, Series or Single)
- The load.
Repeats
I shall be repeating each experiment 3 time. This shall be sufficient in order to produce accurate and reliable results. Also I shall be taking 10 readings. These shall be from 100 grams to 1000 grams. This should produce a wide range of results of which can be plotted onto a graph and an average be taken.
Safety
I will ensure that all loads are safely succoured onto the spring, clamp and stand. Basic lab safety should be enforced such as clear walk ways and hair tied back. Also in case the spring “snaps” back goggles should be worn to protect the eyes from the spring. To prevent a snap back reaction, the mass maximum should not be exceeded. 2 kilogram masses must be placed on the clamp and stand so that it will not topple over when the masses are added to the spring.
Analysis of preliminary experiment
We encountered problems when we were half way through our experiment. When we reached an added weight of 800 grams the clamp and stand toppled over because the clamp and stand was too light. In order to counter this we added 2 kilogram weights to the stand of the clamp this stopped it toppling over.
After our experiment we weighed our masses and found that none of them were exactly 100 grams. They were 1 or 2 grams lower than the presumed 100 grams. This was because they were old weights and parts of them had chipped off
