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Chapter 10 Gravitation Solutions

Question - 31 : - Why does a block of plastic released under water come up to the surface of water?

Answer - 31 : - Two forces act on an object immersed in water. One is the gravitational force, which pulls the object downwards, and the other is the buoyant force, which pushes the object upwards. If the upward buoyant force is greater than the downward gravitational force, then the object comes up to the surface of the water as soon as it is released within water. Due to this reason, a block of plastic released under water comes up to the surface of the water.

Question - 32 : -

The volume of 50 g of a substance is 20 cm3. If the density of wateris 1 g cm−3, will the substance float or sink?

Answer - 32 : -

Ifthe density of an object is more than the density of a liquid, then it sinks inthe liquid. On the other hand, if the density of an object is less than thedensity of a liquid, then it floats on the surface of the liquid.

Here, density of the substance = 

Thedensity of the substance is more than the density of water (1 g cm−3). Hence, the substancewill sink in water.

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