If an object had a mass of 5 kilograms, what would be the weight of the object measured on a spring scale in the unit of newtons?

Weight is a  unit of force.

Newtons measure force.

5 kg is a mass and is in kg. Kg and mass are independent of location. 5 kg is 5 kg on the moon, here on earth, on Jupiter and on Mars or anywhere else you care to name.

F = m*a

F = 5 * 9.81

F = 49.05 Newtons. This is how things should be weighed on planet earth.

answer: 2×10^-2kg

explanation: density= mass per volume

vol=mass/density

converting to s.i units we have;

3÷1000kg = 0.003

1.5÷100m = 0.15

0.003/0.15 = 0.02kg