Question

B.
Give reasons for the following statements.
1. Water droplets appear on the outer surface of a glass full of cold wate
2. One side of the iron girdles of bridge are placed on rollers.
3. A normal glass tumbler cracks when dipped in boiling water.​

Answer 1

Answer:

1)The water vapour present in air, on coming in contact with the cold glass of water, loses energy and gets converted to the liquid state, which we see as water droplets. 

2)when we have rollers at one end then it is allowed to expand freely without any thermal stress.in summers the bridges may expand due to the increase in the temperature and in winters the bridges may compress due to decrease in the temperature.

3 )The crack is caused by differential thermal expansion. The part of the glass that the boiling water touches first expands due to the heat, but the heat doesn't conduct through the glass quickly so there is stress between the expanded inside of the glass and unexpanded outside of the glass.

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Answer 2

Answer:

1- The water vapour present in the air, on coming in contact with the cold glass of water, loses energy and gets converted to a liquid state (gets condensed), which can be seen as tiny water droplet

2-when we have rollers at one end then it is allowed to expand freely without any thermal stress.in summers the bridges may expand due to the increase in the temperature and in winters the bridges may compress due to decrease in the temperature.

3-The crack is caused by differential thermal expansion. The part of the glass that the boiling water touches first expands due to the heat, but the heat doesn't conduct through the glass quickly so there is stress between the expanded inside of the glass and unexpanded outside of the glass.