How would your present weight change if earth had twice the mass that it does now?

The weight would be doubled

Explanation:

The weight of an object on Earth is equal to the gravitational attraction exerted by the Earth on the object:

where

G is the gravitational constant

m is the mass of the object

M is the mass of the Earth

r is the distance between the object and the Earth's center

We see that the weight (F) is directly proportional to the Earth's mass (M): so, if the Earth had twice the mass that it does now (M'=2M), then the weight F would be also doubled, in fact:

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