Chapter 10

NCERT
Class 9
Science
Solutions
5. A mass of 10 kg is at a point A on a table. It is moved to a point B. If the line joining A and B is horizontal, what is the work done on the object by the gravitational force? Explain your answer.

Question:

A mass of 10 kg is at a point A on a table. It is moved to a point B. If the line joining A and B is horizontal, what is the work done on the object by the gravitational force? Explain your answer.

Answer:

Mass m = 10 kg, acceleration due to gravity g = 10 ms–2, work done by the force of gravity = mgh.

In this case the amount of work done by gravitational force on the object will be zero because the line joining the points A and B lie in same horizontal plane.

Its gravitational force does not act any component of displacement. Because it is vertical W = Fs cos 90° = 0.

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