A sphere is resting on two planes BA and BC which are inclined at 45° and 60° respectively with the horizontal. The reaction on the plane BA will be A. Less than that on BC B. More than that of BC C. Equal to that on BC D. None of these

The correct answer is: A. Less than that on BC.

The reaction on the plane BA will be less than that on BC because the sphere will exert a greater force on the plane that is more inclined to the horizontal. This is because the force of gravity will act more directly down on the plane that is more inclined, and the sphere will have to exert a greater force to counteract this force.

Option B is incorrect because the sphere will not exert a greater force on the plane that is less inclined to the horizontal. This is because the force of gravity will act more directly down on the plane that is less inclined, and the sphere will not have to exert as much force to counteract this force.

Option C is incorrect because the sphere will not exert an equal force on both planes. This is because the force of gravity will act more directly down on one plane than on the other, and the sphere will have to exert a greater force to counteract this force on the plane that is more inclined.

Option D is incorrect because the sphere will exert a force on both planes. This is because the sphere is resting on both planes, and the force of gravity will act on both planes.