Introduction

In this science experiment, using Archimedes’ Principle we will learn to establish the relation between the loss in weight of solid when fully immersed in
1. Tap water,
2. Saltwater

Buoyancy

1. The upward force experienced by an object when it is fully immersed in a liquid is called buoyant force or upthrust. And this phenomenon is called buoyancy.
2. Its magnitude depends on the density of a liquid.

Archimedes’ Principle

When a body is fully or partially sunk in a liquid, it experiences an upward force which is equal to the weight of the liquid it displaced.

Application of Archimedes’ Principle

1. In lactometer,
2. In submarines,
3. In hydrometer,
4. Building ships.

Aim

To establish a relation between the loss in weight of solid when fully immersed in
1. Tap water,
2. Saltwater.

With the weight of the water displaced by it by taking two different solids.

Apparatus Required

1. Spring balance,
2. Clamp stand,
3. Two different solids, such as metallic brass bob and rectangular block,
4. Tap water,
5. Saltwater,
6. A strong thread,
7. Two empty beakers.

Theory

When a body is fully or partially sunk in liquid, it experiences an upward force that is equal to the weight of the liquid it displaced.

The loss in weight of the body occurs due to the upthrust.

Loss in weight = Weight of body in the air – Weight of body in liquid.

Loss in weight = Weight of liquid displaced = Upthrust on the body.

Procedure

1. Measurement for the apparent loss in weight of a brass bob.

a. Experiment with tap water

Step 1. Measure the weight of the object and empty beaker with the help of spring balance.

Step 2. Set all the components ( spring balance, overflow can, beaker) as shown below.

Step 3. Immerse the ball completely into the water of the overflow can.

Step 4. Note the reading of spring balance. This is giving you the weight of a brass bob in the water.

Step 5. Now, weigh the beaker that has collected the overflowing water.

Step 6. Weight the displaced water by subtracting the weight of the empty beaker from the weight of the beaker containing overflowing water.

Step 7. Repeat the above steps three times by using the same bob after drying up.

b. Experiment with salty water

Step 1. Take the same solid body used for the experiment a.

Step 2. Take salty water instead of simple water.

Step 3. Repeat the same process from step 1 to step 7.                                   

2. Measurement for the apparent loss in weight of a rectangular block

Step 1. Take a rectangular block instead of a metallic bob.

Step 2. Repeat experiment 1.

Step 3. Repeat the same process of experiment 1 for simple water and salty water.

Step 4. Make a table for it.

Step 5. Do the same experiment two more times.

Observation

1. Zero error of spring balance = ……..
2. Least count of spring balance = ……..
3. Weight of beaker = ………
4. Zero error can be negative or positive.
5. Density of water = 1gm/cm^3

Conclusion

1. We have proved that the apparent loss in weight of solid when immersed in a liquid is equal to the weight of the liquid displaced by it. This confirms the principle of Archimedes.
2. Loss in weight of solid when immersed in salty water is more than the loss in weight of solid when immersed in simple water.

Precaution

1. Zero error of spring balance should be perfectly measured.
2. While taking the spring balance reading, solid should be perfectly immersed in liquid.
3. Beaker should be placed in such a way that all the overflowing water collects in it.
4. Solid-body should not be touching the overflow can’s wall or bottom.

Conclusion

Through this experiment, we have proved Archimedes’ Principle.

Viva Questions with Answers

Q.1 Describe Archimedes’s principle?

ANS. When a body is wholly or partially sunk in liquid, it experiences an upward force which is equal to the weight of the displaced liquid by it.

Q.2 What is upthrust?

ANS.  The upward force experienced by an object when it is fully immersed in a liquid is called buoyant force or upthrust.

Q.3 How many forces act on a body immersed in liquid?

ANS. Two.

Q.4 What are the two forces acting on a body immersed in liquid?

ANS. 1. Gravity by the object,

2. Upthrust (by the liquid on an object)

Q.5 When does a body floats on liquid?

ANS. A body floats on liquid when both the forces of upthrust and gravitational balance each other.

Q.6 What is the weight of liquid displacement?

ANS. The weight of the liquid displaced is equal to the weight of the body immersed in liquid.

Q.7 How will you measure the observed weight of solid?

ANS Observed weight of solid = True weight of solid – Weight of liquid displaced by solid.

Q.8 When the same solid is immersed in two liquids with different densities, in which liquid weight loss is more?

ANS. Greater the density more will be weight loss.

Q.9 Why is it easier to swim in seawater than to swim in any other place?

ANS. Because the density of seawater is more as compared to a swimming pool or river. Also, it exerts more upthrust on swimmers; as a result, it is easier to swim in seas.

Q.10 On what factor does the upthrust depend?

ANS. 1. Density of liquid,

2. Volume of liquid displaced.

Q.11 What is the other name for upthrust?

ANS. Buoyancy.

Vikram Sarabhai

An Indian physicist and astronomer.