An object is taken from a point `P` to another point `Q` in a gravitational field:

Options

A. assuming the earth to be spherical, if both `P` and `Q` lie on the earth's surface, the work done is zero
B. if `P` is on the earth's surface and `Q` above it, the work done is minimum when it is taken along the straight line `PQ`
C. the work done depends only on the position of `P` and `Q` and is independent of the path along which the particle is taken
D. there is no work done if the object is taken from `P` to `Q` and then brought back to `P` along any path

Answer

A, C, D

Explanation

Work done in independent of the path chosen and depends only on the initial and final positions of the object. Also the work done on any closed path in a gravitational field will be zero. Since, every point on the surface of the earth is at the same potential no work is done for points on the surface of the earth. Hence, the correct choices are a,b and d.