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Matter In Our Surroundings
Look at the activities listed below. Reason out whether or not work is done in the light of your understanding of the term ‘work’:
(i) Suma is swimming in a pond.
(ii) A donkey is carrying a load on its back.
(iii) A wind mill is lifting water from a well.
(iv) A green plant is carrying out photosynthesis.
(v) An engine is pulling a train.
(vi) Food grains are getting dried in the sun.
(vii) A sailboat is moving due to wind energy.
(i) Yes, Suma is doing work by pushing water in the backward direction.
(ii) No, because the force exerted by donkey in the upward direction is perpendicular to the horizontal displacement of the load. Hence, no work is done.
(iii) Yes, work is done in lifting water against the force of gravity.
(iv) No, because the leaves of plants remain at rest during photosynthesis.
(v) Yes, engine is doing work in pulling the train. Both the applied force and displacement are in same direction.
(vi) No, because food grains remain at rest.
(vii) Yes, work is done by the wind in moving the sailboat.
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Convert the following temperatures to Kelvin scale
25°C
What is the physical state of water at
100 °C
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
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