# Activity 10.7 Class 9 Science Gravitation

Activity 10.7 Class 9 Science Gravitation Chapter 10

Activity 10.7 asks us to tie a stone with a rubber string and compare the length of the string when the stone is in water and when it is in the air.

#### Observation:

The length of the rubber string is lesser when the stone is inside the water.

#### Explanation:

The liquid medium exerts an upthrust force on the submerged objects. This force is proportional to the volume of fluid displaced.and is called the Buoyant force.

The length of the string is the stress on the string due to the weight produced by the stone. An upthrust force on the stone reduces this stress.  As a result, we see a reduction in the length of the rubber string.

#### Facts:

The buoyant force is proportional to the density of the fluid medium. We use this property to detect the purity of various fluids like milk, precious metals in molten state, etc.

Next: Work and Energy Activity.

Ref: Chapter 10.

Activity 10.7 Class 9 Science Gravitation Chapter 10

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