On the moon the acceleration due to gravity is 1.6 ms if an object has a mass on earth of 5.1kg what is its mass on the moon

Mass on the moon is 5.1 kg.

Explanation:

Given mass on earth = 5.1 kg

acceleration due to gravity on moon = 1.6 ms⁻².

The mass on the moon does not change because mass is the quantity of matter in the body regardless of its volume or  of any forces acting on it.

Whereas the weight of the object changed.

Weight is the the force exerted on a body which is related to mass and expressed as W = mg.

W = weight of object   m = mass of object      and g = gravitational force

N stands for newton unit of weight.

Thus mass of the object on moon is same as on earth which is 5.1 kg.