Preliminary Results
Things I will use
- Gas jar
- Plasticine (27.5g)
- Thread
- Weighing scales
- Paper towels
- Sun flowers oil
- Stop watch
In my final experiment I will
- Weight out plasticine to 0.5g, 1g, 1.5g, 2g, 2.5g, 3g, 3.5g, 4g, 4.5g, 5g.
- Attach enough thread to each plasticine amounts so that the plasticine reaches the bottom with excess.
- Roll into a sphere
- Fill a gas jar with sun flower oil
- Place the gas jar on top of some paper towels
- Get the stop watch and another person to drop the plasticine into the oil and the first weight ready.
- Drop the plasticine in the oil and as the bottom hits the oil’s surface start the timer
- when the plasticine hits the bottom of the gas jar stop the stop clock
- record results
- repeat this weight and shape 9 more times
- repeat this experiment with the other 9 weights
To make this a fair test I will measure the spheres accurately, repeat each weight 10 times and dry the plasticine after each use. The preliminary work has helped me make this method because I now which shape and weights to use. I will only change the weight of the plasticine and will keep the shape, amount of oil it will fall thought and the other items used.
My prediction is that the heavier the plasticine the faster the decent and the lighter the object the slower the Decent. I think that terminal velocity will be hard to measure because the gas jar is only 27cm tall so the plasticine may still be accelerating at the bottom of the gas jar. Terminal velocity is where the forces acting on an object are equal. You measure terminal velocity by, recording the time it takes for an object to move X distance in at total distance of Y over and over again, for example if a sky diver falls 10,000 meters measure how long it took them to fall the first 100 meters then the next 100 meters and so on. Then you can work out the speed of the object (in the example sky diver) for each interval when the speeds stay steady at Z m/s that is the terminal velocity. I also think that the shape of the plasticine will make a big difference because there will be less drag on a spherical shape than on a disc so. The force acting down on the shapes will be the same because the gravity will not change. An example of where this may be tested is for submarines to what shape will be best to cut thought the water by the smallest force.
To work out the averages I added up the ten results and then divided that by ten this gave me the mean time and to work out the average speed I took the length of the gas jar (27cm) and divided it by the mean time.
A Graph Showing Ave Speed : Weight of Plasticine
A Graph Showing Ave Time : Weight of Plasticine
my graphs show me that if an object is heavier than another it will reach a greater speed and will fall faster, so the relationship between mass and speed is the greater the mass the faster it will fall and the relationship between mass and ave. time is the greater the mass the less time it will take to fall. This is because the force of gravity acting on the heavier sphere is greater than if the mass is smaller, even thou the bigger spheres have more surface area to create drag.
My method was clear but I did not take into account whether human error came into play because I could of stop the watch to soon or too late. If I was to re-do this experiment I would have an electronic counter to get the results more accurate. Some of my results therefore could be out for example when looking at speed : mass the result 3.5g is lower than it should be meaning that I under timed. I can not work out the terminal velocity because I do not have sufficient data to do so, if I was to redo this investigation I would measure the distance that the plasticine travelled after X seconds but this would mean having a taller gas jar so that I could get the number of results I need. So the conclusion I did may not be completely reliable.
