Question

Weight of object at earth surface is 10 kg. Find the weight of object at the centre of earth?

Answer 1

Zero

Explanation:

Modelling the Earth as a spherical body with uniform density and the object as a particle, the weight of the body varies linearly as the distance of the particle from the geometrical center of the sphere. At the center its weight is zero. Or you can argue by symmetry: if the weight is not zero, in what direction would it act?

Answer 2

0kg, 10kg, or 0 newtons depending on how technical you want to get and what the question is really trying to ask.

Explanation:

A weight is not technically measured in kg. It is measured in newtons. Weight is a force. Kilogram is a measure of mass, not force. An item with 10kg of mass would weight about 98.1 newtons on the surface of the earth. It would weight 0 newtons at the center of the earth. It would still be 10kg of mass, though.

Many people use the term kg as though it is a measurement of weight. If that is the case for your level of study, the expected answer to the question would be 0kg.

Consider the question "How much does the Earth weigh?" Then, once you have an answer, ask "How much would it weigh at the center of the Earth?" The Earth is already at the center of the Earth, so if you answer 0kg to the question about the 10kg item, you would also have to answer 0kg to the weight of the Earth! I hope this paragraph doesn't confuse you, it is just meant to show that weight is a force that (when you get really technical about it) is not measured in kg.