Question

An object on earth has a mass of 4 kg. calculate its weight on another planet that has an acceleration due to gravity one-half that of the earth.

Answer 1

Relatively the same work as what Al2006 did, just round off the answer to 20 N.

So,

w₂ = 19.6 ≈ 20 N

Answer 2

Weight = (mass) x (acceleration of gravity)

-- Acceleration of gravity on Earth = 9.8 m/s²
-- Acceleration of gravity on Planet-Q = 4.9 m/s²

Weight on Planet-Q = (4 kg) x (4.9 m/s²) = 19.6 newtons .