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Matter In Our Surroundings
Question
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Define the term work. State the conditions that need to be satisfied for work to be done. Give some situations in which work is done.

Answer

Work is the amount of force exerted on a body such that it moves in the direction of the force. 

Two conditions need to be satisfied for work to be done are as follows: 

(i) A force should act on the body. 

(ii) The body must be displaced in the direction of the applied force. 

Work is not done, if either of the above two conditions is not satisfied.

Let consider some examples from the daily life. 

(i) Push a pebble lying on a surface. The pebble moves through some distance. Here we apply a force on the pebble and the pebble gets displaced. So, we have done work on the pebble.

(ii) We apply a force to lift a book through a height. The book rises up. We have done work in moving up the book.

(iii) A bullock is pulling a cart. The cart moves. There is a force on the cart and the cart has moved. The bullock has done work on the cart.

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Some More Questions From Matter In Our Surroundings Chapter

For any substance, why does the temperature remain constant during the change of state ?

Suggest a method to liquify atmospheric gases.

Convert the following temperatures to Kelvin scale.

35°C

Give reason for the following observations.

Naphthalene balls disappear with time without leaving any solid.

Give reason for the following observations.

We can get the smell of perfume sitting several metres away.

What is the physical state of water at

a) 25°C
b)00C
c)1000C

What is the physical state of water at
0°C

What is the physical state of water at
100°C

Give two reasons to justify
Water at room temperature is a liquid.

Give two reasons to justify
An iron almirah is a solid at room temperature.