7. Complete Activity 9.7 (Page 109).
• Take a piece of stone and tie it to one end of a rubber string or a spring balance.
• Suspend the stone by holding the balance or the string as shown in Fig. 9.6 (a).
• Note the elongation of the string or the reading on the spring balance due to the weight of the stone.
• Now, slowly dip the stone in the water in a container as shown in Fig. 9.6 (b).
• Observe what happens to elongation of the string or the reading on the balance.
Answer:
Aim: To observe how the reading changes when the stone is dipped in water and conclude based on that.
Materials Required: Spring balance, thread, stone, water, beaker.
Procedure:
(i) Using the piece of thread tie the stone to the spring balance.
(ii) Suspend the stone from the balance and note the reading.
(iii) Now gently submerge the stone in water in the container and note the reading.
Observations:
You will find that the elongation of the string or the reading of the balance decreases as the stone is gradually lowered in the water. However, no further change is observed once the stone gets fully immersed in the water.
Conclusions:
- This proves that a force called buoyant force acts on the stone in upward direction.
- As the stone is being lowered into the water, the buoyant force acting upwards on the stone gradually increases and hence the reading decreases.
When the stone gets fully immersed in the water, the buoyant force remains the same, hence the reading does not change.
“Take a piece of stone and tie it to one end of a rubber string or a spring balance.
Suspend the stone by holding the balance or the string as shown in Fig. 9.6 (a).
Note the elongation of the string or the reading on the spring balance due to the weight of the stone.
Now, slowly dip the stone in the water in a container as shown in Fig. 9.6 (b).
Observe what happens to elongation of the string or the reading on the balance.” – Solved.
Related Links:
Solution to Activity 9.1
Solution to Activity 9.2
Solution to Activity 9.3
Solution to Activity 9.4
Solution to Activity 9.5
Solution to Activity 9.6
Solution to Activity 9.7
Solutions to Chapter 9 Gravitation
