Explain the practical of archimedes's principle with some precaution .

AIM
To establish the relation between the loss in weight of solid when fully immersed in

1. tap water
2. strongly salty water, with the weight of water displaced by it by taking at least two different solids.

APPARATUS REQUIRED
A spring balance, a clamp stand, two different solids, such as metallic brass bob and rectangular block, overflow can, tap water, strongly salty water, a strong thread and two empty beakers.

THEORY
According to Archimedes’ principle, when a body is immersed in a liquid, completely or partially, it loses its weight. The loss in weight is equal to the weight of liquid displaced by the body.
The loss in weight of a body is due to the presence of upthrust which is equal to the weight of liquid displaced. Thus,
Loss in weight = Weight of body in air – Weight of body immersed in water
=W – W₁
= Upthrust in water on the body
= Weight of liquid displaced.
PROCEDURE

(A) Measurement for the apparent loss in weight of brass bob:

(a) Experiment with tap water:

1. Measure the weight of a solid, say a metallic ball in air by using spring balance as shown in Fig 3.1 and as per procedure explained in Experiment 2 of Term II.
2. Weigh the empty beakers using spring balance.
3. Set the spring balance, overflow can with tap water and beaker as shown in Fig 3.2.
4. Now, allow the bob to immerse completely in water in overflow’ can.
5. Note down the new position of pointer of the spring balance. This will give you the weight of the brass bob in tap water.
6. Weigh the beaker containing displaced water which is collected from the overflow can while immersing the bob in it completely.
7. Find the weight of displaced water by subtracting the reading of step (2) from step (6). The weight of liquid displaced is equal to the upthrust. Therefore, the weight of displaced water would be equal to the loss of weight in the brass bob.
8. Repeat the above steps two more times with the same brass bob after drying up completely. Tabulate your observations in Table A.

(b) Preparation of strongly salty water:

9. Take a beaker of capacity 500 mL and pour 300 mL of tap water into it.
10.Dissolve the common salt (known amount) by stirring with the help of a glass rod till the saturation state of the solution.

(c) Experiment with salty water:

11. Again take the same solid body (i.e., brass bob) and repeat the steps from (1) to (8) with strongly salty water.
12.Tabulate your observations in Table B.

(B) Measurement for the apparent loss in weight of second solid body:

1. Take a different solid body such as a metallic rectangular block given by your teacher.
2. Repeat the experiment in the same manner as done for the measurement for the apparent loss of weight of brass bob in tap water and salty water.
3. Make a separate table for the second given body similar to Tables A and B.
4. Tabulate your observations.
5. Repeat the experiment for two more times.

OBSERVATIONS AND CALCULATIONS
Zero error of the spring balance, e -=  …………… g wt.
Least count of spring balance =  …………… g wt.
Range of spring balance =  …………… g wt.
Density of water = 1 gm cm^-3
Weight of empty beaker (Wb) =   …………… g wt.

Table A: Verification of apparent loss in weight of solid body in tap water

For negative zero error, zero correction = (W’₁+e) g wt

Table B: Verification of apparent loss weight of solid body in salty water

CONCLUSION

1. The apparant loss in weight of solid immersed fully in liquid (tap water and salty water) is equal to the weight of liquid displaced by that body. This also proves Archimedes’ principle.
2. Loss of weight in the strongly salty water is more as compared to that of tap water for the same solid
   body.

PRECAUTIONS

1. The zero error (if any) of the spring balance should be noted accurately.
2. A stable, sensitive and zero error free spring balance should be used.
3. Solid body should be immersed fully in tap water/strongly salty water not partially while taking the spring balance reading.
4. Solid body should not touch the side or bottom of the overflow can.
5. There should be no air bubble present inside the water or salty solution while immersing the solid body.
6. Care must be taken while solid body is allowed to immersed in tap water/salty water so that tap watert & salty water does not splash out.