Question

If a rock is 70 kilograms what is its weight on earth

Answer 1

Weight = mass × gravity

Earth: 

W = 70 × 9.8

= 686 Newtons

Answer 2

Weight = (mass) x (gravity)

Gravity on Earth is 9.8 m/s² .

The weight of 70 kg of mass on Earth is 

(70 kg) x (9.8 m/s²) = 686 newtons  (about 154.3 pounds)