Ans 1: (Master Answer)
Mass is the amount of matter present in an object whereas weight is the force exerted by the gravity on that object.
Now, the weight of an object, W = g X m, where 'g' is Earth's gravitational constant and 'm' is the mass of the object.
The weight of the object will remain constant as long as the mass of that object is not changing since 'g' is constant. However, the weight of an object can still be changed without changing the mass. This can be explained by the following example: Consider a helicopter with a mass, 'm'.
1. If the helicopter is accelerated towards the earth (during landing) with an acceleration equals to 'A' (positive acceleration) then its weight would become, W = (g + A) X m, and hence, the weight would increase.
2. If the helicopter is accelerated away from the earth (during take-off) with an acceleration equals to '- A' (negative acceleration) then its weight would become, W = (g - A) X m, and hence, the weight would decrease.