Question

What will be the weight of a box, mass 10Kg on the surface of a hypothetical planet having mass double of Earth and the radius is 3 times of Earth

Answer 1

Answer:

           W ’= 21.78 kg

Explanation:

The expression for weight is

          W = m g

let's look for the acceleration of gravity with the universal law of gravitation

          F = G m M / r2

          F = m (G M / r2)

without comparing the two equations

          g’= G M / r2

in that case M = 2 Mo and r = 3 ro

where mo and ro are the mass and radius of the earth

         we substitute

         g ’= G 2Mo / (3r₀) 2

         G ’= 2/9 G Mo / r₀²

         g ’= 2/9 g

the weight of the body on this planet is

         W ’= m g’

          W ’= m 2/9 g

let's calculate

          W ’= 2/9 10 9.8

           W ’= 21.78 kg