Fun With Archimedes' Principle

Yesterday lesson 'Application of Archimedes' Principle" with 4Setia was fun. By the end of the lesson my dear 4Setia knew that this principle is used in the rising/diving of a submarine, ascending/decending of a hotair balloon and in a hydrometer.

Interesting activity on creating a 'hot air balloon' by Samantha & Bernard of 4Setia 2011...

I wonder can anybody suggest a better way to make sure the hot air balloon they created fly upright?

From Chapter 3 (Forces & Pressure):

Archimedes' Principle  states that 

For any object (fully/partially) immerse in fluid (liquid/gas),
"Buoyant Force = Weight of fluid displaced"

From Chapter 2 (Forces & Motion):
a) If the object is floating, the net force = 0 since it is stationary
So "Buoyant Force = Weight of the object"

b)If the object is sinking/decending, net force is not zero
So "Buoyant Force < Weight of the object"

c)If the object is rising/ascending, net force is not zero
So "Buoyant Force > Weight of the object"

Means that in order to solve problem involving this principle,

 we need to really understand the definition & relate it to net force....

Experiment 3.1 

To determine the relationship between the weight of water displaced and the buoyant force

4Amanah 2011

Kevin, Michelle, Edwin, Jacelyn...

The result:

where 

a - Weight of the object in the air

b - Weight of the object in the water (Apparent Weight of the object)

c - Weight of the empty beaker

d - Weight of the beaker and the displaced water

e = apparent loss in weight = Buoyant Force = a - b

f = weight of displaced water = d - c

So from the table above, which group is the winner?

Haa...well done to group 5 & 6  for ur success in proving the Archimedes' Principle!

'Mimi Chocola', Zulfikar & Brenda...happy faces :)
I love to see students smiling faces..

Problem Solving

Format: Paper 2 (Section B)

Diagram 1 and 2 show two identical hydrometers are used to measure the density of Liquid P and Q.

Observe the diagrams and compare the followings:

1. The weight of the hydrometer.

2. The buoyant force acting on the hydrometer.

3. The level of the hydrometer (float higher/lower)

4. The volume of liquid displaced

5. The Weight of liquid displaced

6. The density of the liquid

Hence, State the relationship between the density of the liquid and the volume of liquid displaced.

Inventing A Hydrometer

4 Setia's students with their successfully made hydrometer using test tube, cotton & ball bearing.

Hydrometer is an instrument used to measure the density of a liquid.

Now my question are:

1. How are u going to callibrate ur hydrometer?

2. How to increase the sensitivity of a hydrometer?

3. What is the best material can be use to create a hydrometer, 

if it is use to measure the density of an acid?

Samantha, Siti Zubaidah, Megan & Victoria...

Annabelle, Joshua, Diyana, Derek....

Munirah, Haidah, Tan Xin Tian, Bernard, Ethel