Identify in each case whether work done in each case is negative, positive or zero by givingappropriate reason in support of your answer (in notebook)-(i) Work done by the gravitational force of earth acting on a satellite moving around it in acircular path(ii) A man of 60 kg carrying a luggage of 80 kg on his head waiting for the train on platform.(iii) A squirrel going up a tree.(iv) An engine is pulling coaches of train.(v) A body falling freely due to force of gravity
Question
Identify in each case whether work done in each case is negative, positive or zero by givingappropriate reason in support of your answer (in notebook)-(i) Work done by the gravitational force of earth acting on a satellite moving around it in acircular path(ii) A man of 60 kg carrying a luggage of 80 kg on his head waiting for the train on platform.(iii) A squirrel going up a tree.(iv) An engine is pulling coaches of train.(v) A body falling freely due to force of gravity
Solution
(i) Work done by the gravitational force of earth acting on a satellite moving around it in a circular path: The work done by the gravitational force of the earth on a satellite moving around it in a circular path is zero. This is because the gravitational force is perpendicular to the direction of motion of the satellite. In this case, the force and displacement are at right angles to each other, resulting in zero work done.
(ii) A man of 60 kg carrying a luggage of 80 kg on his head waiting for the train on platform: The work done in this case is zero. When the man is waiting for the train on the platform, there is no displacement in the direction of the force. Therefore, no work is done as the force and displacement are perpendicular to each other.
(iii) A squirrel going up a tree: The work done by the squirrel going up a tree is positive. This is because the squirrel is exerting a force against gravity in the upward direction, and there is a displacement in the same direction. The work done is positive as the force and displacement are in the same direction.
(iv) An engine is pulling coaches of a train: The work done by the engine pulling the coaches of a train is positive. The force exerted by the engine is in the direction of the displacement of the coaches. Therefore, the work done is positive as the force and displacement are in the same direction.
(v) A body falling freely due to the force of gravity: The work done by the force of gravity on a body falling freely is negative. This is because the force of gravity acts in the downward direction, while the displacement of the body is in the upward direction. As the force and displacement are in opposite directions, the work done is negative.
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