Group 4 description
Introduction
Our Group (H) is composed by 4 members: Marianna Vincenti, Indrie Cesario, Michael Di Rienzo and Cristian Ying. For the project we thought of making a toy boat for bath tubs, which was going to be powered by air from a balloon placed on the back of the boat. We also did a buoyancy test with different materials in order to find the best one to build the boat with. In the end we used “Styrofoam” and “Plastic packing material”, because they were the less dense and floated better than the others. Then we built them and tested them on water. Aims:
- To find the most buoyant material out of a selection, and the most suitable to build a children’s floating toy.
- To use the two most buoyant materials to construct three toy boats which floated and moved.
- To investigate the best combination of shape and material in constructing the toy boats; using speed and buoyancy as factors.
Part I
We started by researching the most buoyant materials out of the ones we collected (on the table on the side), so that we could find out which was the most adapted to building the toy boat. We began with the assumption that the water we were using at room temperature had a density (mass per unit volume) of 0.99g/cm3, and calculated the densities of all the materials which were being tested to make a prediction of which one would float most easily. To do this we measured the mass in grams of each material and divided it by the volume of each sample, which we found by filling a beaker with water, dropping the object inside and measuring the amount of water displaced by the submerged sample. We predicted that the materials with the lowest density would float best, since they allowed the force of upthrust in water to work more efficiently. Based on the table of densities on the side, we predicted that Styrofoam, plastic packing and Balsa wood would be the most buoyant since their densities are the smallest. We then tested our prediction by placing the objects in a trough of water and observing what happened and repeated the experiment twice for accuracy. The result, both in our predictions and observations, was that the most buoyant materials were Styrofoam and a plastic packing material.
We could have improved this part of the experiment by repeating the measurements for each sample at least three times, giving us a more accurate result and a wider range of data which would have allowed us to observe any anomalies clearly. We should also have ensured that all the objects being sampled were the same shape and size, so that there would have been less variables affecting our data. However seeing as the objects were not the same shape, we found that the best way of measuring their volumes was in fact the one we used. This is because by using water displacement to measure volume, all the irregularities in the samples’ shapes were included in our measurements.
Part II
We then used the two most buoyant materials (Styrofoam and a plastic packing material) to make three sample toy boats, of two different shapes. Then we investigated which shape and material made for the best toy boat, basing our decision on their buoyancy and speed when propelled by a balloon filled with a fixed amount of air. Because the toy is aimed at small children, we built the toy as a flat platform so that it could support more weight and float more easily, making it more fun to play with. Also, in this way the weight of the material is spread out in a larger surface area, making it harder for a child to swallow and therefore less dangerous.
-We began by making sure that all the toy boats were the same weight: 18.00g. In this way, we eliminated a variable and made our results more reliable.
-Firstly, we measured their buoyancy. We floated them in a trough full of a given quantity of water and counted the amount of metal weights it took to sink it.
-The weights were placed on top of the boats, which were all the right way up and in still, unmoving water. To ensure that the boats’ capability was completely full, we continued placing weights onto the boat until it capsized, then counted the number of weights at the bottom of the trough.
-We repeated the experiment three times to make the results precise and then took an average of the three, shown in the table below.
-To make the experiment more accurate, we could have put the weights on the same place on the boat each time the test was repeated. However, by changing the arrangement of the weights we were able to measure the maximum capability of the boats.
- In conclusion, we found that the circular shaped boat was unstable compared to the house shaped one of the same material (plastic packing). As well as being less balanced and stable, it held significantly less weights before sinking than the house shaped boat.
-When we found the best shape for the boat’s stability and buoyancy, we made another one using the same ‘House’ shape, but using Styrofoam; the next best floating material found in our previous experiment. We then used this new boat to test the difference in buoyancy between two boats of equal shape and mass, but different material.
-Our results showed no significant difference between the two, though the plastic packing material one supported a minimal amount more.
Part III
-Using a baby pool, we tested the velocities of the three toy boats in water. To do this, we attached at the back of the boat a thin, lightwood stick and to that, a balloon.
-We experimented to find the best way of attaching the balloon before we began collecting data, and found that the most efficient was to have the opening of the balloon in the water and facing away from the back of the boat, so that the air expelled from the balloon propelled the toy forwards. The bulk of the balloon was kept outside, to reduce drag and increase the ease with which the boat slid on the water, and therefore its speed.
-We measured the amount of time it took for the boat to travel across the baby pool, which was 1m in width, having filled the balloon until it was approximately 20cm in diameter. We then used these to calculate each boats’ speed. The test for each boat was repeated three times to check for anomalies and to enable us to find an accurate average.
- All the boats started from the same point, marked on the edge of the pool, and with the back of the balloon already in the water, so that the full push of air was taken advantage of.
-In conclusion, we found that the Styrofoam house shaped boat was the fastest. However, to make the test more accurate, we could have made the shaped of the boats more accurate, since we found that the plastic packing ‘house’ shaped boat, though it carried the most weight, had a slightly crooked point so spun in circles rather than going straight across the pool. This meant that we could not accurately measure the speed of that particular boat, and affected the reliability of our results.
Conclusion
As a conclusion to our experiments, we asked children from the junior school from Red Dragons to year 3 and from year 4 to Year 6 to vote on their preferred shape/design of toy, which was the circular boat in both age groups.
We also had to find a way to decide how to combine the results from parts II and III of our experiment to decide which was the ‘Ultimate’ combination of material and shape to produce the ‘Ultimate’ toy boat. We therefore put it up to the children to decide between the toy’s speed and the toy’s buoyancy as our deciding factor. As can be seen by the tables showing the votes, in both age groups the preferred quality in a bathtub toy was speed rather than buoyancy. Therefore a good compromise, for the perfect toy boat, could be to produce a circularshaped Styrofoam boat, Styrofoam having been the fastest material tested. Although the circular shaped was shown in part I to not be very buoyant, this could be an extension to our experiment: to find a way of producing a circular boat which has the capability of holding as much weight as the two house shaped ones.
Videos of Test on water:
http://www.youtube.com/watch?v=LL2Ur0AyRog
http://www.youtube.com/watch?v=hnKMfbIgVMw
http://www.youtube.com/watch?v=0N-7CHMM8P4
Data collected from variouse experiments.
Pictures taken during the Group 4 week!
