Photos

A few photos of me doing my experiment..















Pouring water into the container

Floating an empty container















Weighing 50 g of flour

Results

29/5/10: Got my first set of results for part A today.

1. Water level: 3.5 cm
0 g - 0.2 cm below
+50 g - 1.1 cm below
+100 g - 1.9 cm below
+150 g - 2.4 cm below
+200 g - 3 cm below
+250 g - sunk

1/6/10: Second and third sets of results for part A.

2. Water level: 3.5 cm
0 g - 0.1 cm below
+50 g - 1 cm below
+100 g - 2 cm below
+150 g - 2.7 cm below
+200 g - 3.5 cm below
+250 g - sunk

3. Water level: 3.5 cm
0 g - 0.1 cm below
+50 g - 1.4 cm below
+100 g - 2.2 cm below
+150 g - 2.8 cm below
+200 g - 3.5 cm below
+250 g - sunk

5/6/10: Got all three sets of results for Part B throughout today.

1. 0g - sunk
+50 g - 0.2 cm above
+100 g - 0.6 cm above
+150 g - 0.8 cm above

2. 0g - sunk
+ 50 g - 0.3 cm above
+100 g - 0.7 cm above
+150 g - 1 cm above

3. 0 g- sunk
+50 g - 0.2 cm above
+100 g - 0.4 cm above
+150 g - 0.7 cm above

Method

Now that my experiment is approved, it's time to write my method. Lovely. So there will be two parts to my experiment which ultimately prove the same result, as explained in my last post.

PART A - Investigating how the mass:volume ratio of an object affects its buoyancy:
1. Fill a clear rectangular container of dimensions 30 cm by 20 cm by 8 cm with 2.5 L of water.
2. Place an empty circular plastic container inside.
3. Observe and record whether it is afloat, sunk or partially afloat and to what degree.
4. Take out circular container and add in 50 g of flour.
5. Put circular container back inside rectangular container.
6. Observe and record whether it is afloat, sunk or parially afloat and to what degree.
7. Repeat steps 5-6 until the circular container sinks completely to the bottom, recording results each time.
8. Repeat steps 1-8 a further two times.

PART B - Investigating how the density of fluid affects buoyancy.
1. Fill a clear rectangular container of dimensions 19 cm by 12 cm by 6 cm with 500 mL of water.
2. Place plastic circular container containing 150g of flour in.
3. Mark and record position of circular container in rectangular container.
4. Take out circular container and pour out water from rectangular container.
5. Heat 500 mL of water and dissolve 50 g of salt in it.
6. Allow water to cool and then pour into rectangular container.
7. Put circular container back inside rectangular container.
8. Observe and record whether it is afloat, sunk or partially afloat and to what degree.
9. Repeat steps 4-10 twice, dissolving 50 g more salt than the previous time, recording results each time.
10. Repeat steps 1-10 a further two times.

** Note that quantities of flour and salt may be altered slightly before I officially start experimenting. (If I find that a different quantity will make the experiment more efficient or effective, and produce more accurate results.)

Ta-da! And there we have it, 1 of 150 methods for you to look through. Have fun marking, Miss Zhang! ;)

Buoyancy Explanation

Ok, so basically buoyancy is defined as the upward force of water which allows objects to float. This force is exerted when an object is placed in water. The water level rises, and is displaced in a volume equal to that of the object.

For an object to completely float, the weight of the displaced water must be greater than that of the object. Therefore, dense objects will most likely not float. The reason objects are more buoyant in salt water than fresh water is that water containing dissolved salt in it is heavier. This means a greater mass of water is displaced, hence exerting a greater upward force, and causing an object to float.

So I can see two ways of testing buoyancy. I can compare the results of experimenting with objects of a differing mass:volume ratio, or I could simply change the amount of salt in the water. Or I could do both. Both experiments prove that buoyancy is determined by the mass of water displaced in relation to the mass of the object.

Climatic Graph

Yay! So I finished doing my climatic graph, editing it with paint no less. At least it's decent.. I hope.

Buoyancy Factors

Did a bit of research. So apparently buoyancy is affected by the following three factors:
*density of fluid
*volume of fluid displaced
*local acceleration due to gravity

Depth

I had a feeling my experiment might be too simple, but I'm not sure how to improve on that. Would broadening it to all of the factors (rather than just one) which affect buoyancy 'deepen' my experiment?