Chapter 09 Gravitation Questions-04
Questions
1. Why is it difficult to hold a school bag having a strap made of a thin and strong string?
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Answer
It is difficult to hold a school bag having a thin strap because the pressure on the shoulders is quite large. This is because the pressure is inversely proportional to the surface area on which the force acts. The smaller is the surface area the larger wold be the pressure on the surface. In the case of a thin strap, the contact surface area is very small. Hence pressure exerted on the shoulder is very large.
2. What do you mean by buoyancy?
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Answer
The upward force exerted by a liquid on an object that is immersed in it is known as buoyancy.
3. Why does an object float or sink when placed on the surface of water?
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Answer
If the density of an object is more then the density of the liquid then the object would sink this happens because in this case buoyant force that is acting on the object due to liquid is less than the force of gravity acting on the object. If the density of object is less than the density of the liquid, then it floats on the surface of the liquid, this happens because the buoyant force acting on the object is greater than the force of gravity.
