Question

How does gravity affect weight?

Answer 1

As a first step, you could briefly explain the concept of weight of an object. Then you could explain how it is related to the gravitational field and hence the gravity. In addition, you could also clarify how weight is different from the mass of an object and also the relation between these entirely different quantities.

Complete solution:
In the question, we are asked how gravity affects the weight of an object. In order to answer this question, one should be thorough with the concept of weight.

Weight could be defined as the force on an object with some mass and which is under the influence of a gravitational field. Though you may often confuse yourselves between mass and weight, they are actually very different concepts.

One thing that you can be always sure of is that all objects that have mass under the vicinity of a gravitational field experience a force that is weight. Also, the more the mass of an object is the stronger will be this force. Weight of an object or in other words the gravity force on a object can be given by,
$W=mg$
Where, m is the mass of the object and g is the gravitational field strength or the acceleration due to gravity.

So, we see that mass and weight are directly proportional to each other for a given gravitational field strength.

Also, the gravitational field strength at distance r could be given by,
$g=\dfrac{GM}{{{r}^{2}}}$

Consider the case of Earth, the closer an object is to the centre of the earth, the smaller will be r, the greater will be g and thus the greater will be its weight. So when r is increased, g as well as the weight will also be small.

Note:
In the solution, we haven’t stressed upon the term ‘mass’ though we have made it very clear that it is very different from weight of an object. Mass is actually the measure of the amount of substance contained within a body which will be the same irrespective of where they are. That is, the mass of an object is the same on the moon as well as the earth.