Look at the activities listed below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.
•Suma is swimming in a pond.
•A donkey is carrying a load on its back.
•A wind mill is lifting water from a well.
•A green plant is carrying out photosynthesis.
•An engine is pulling a train.
•Food grains are getting dried in the sun.
•A sailboat is moving due to wind energy.
Answers
Answer:
1) yes
2) No
3) Yes
4)No
5) yes
6) No
7) yes
Explanation:
1) Suma is swimming in a pond and hence moving towards a certain direction (say horizontally) , so work is done.
2) When the angle of object and displacement is 90degrees, no work is done, so no work is done by the donkey.
3) Windmill is doing work here , since water is lifted against gravity.
4) No work is done during photosynthesis since no energy transfer is taking place.
5) Work is done since a force is exerted by the engine and the train moves in that direction.
6) No work is done during drying of food grains in sun. Net transfer of energy is zero.
7) Wind is carrying the sailboat in certain direction. So wind is doing the work.
Answer:
Suma is swimming in a pond. - This is work as she is using force to move ahead.
A donkey is carrying a load on its back. - This is not a work. Since the force and displacement is 90 degree.
A wind mill is lifting water from a well. - This is work done. The lifting is done against force of gravity.
A green plant is carrying out photosynthesis. - This is not a work.
An engine is pulling a train. - Since the engine is applying force to pull the train, this is considered to be a work.
Food grains are getting dried in the sun. - No work is done by sun.
A sailboat is moving due to wind energy - Work done by air, since it exerts a force.