Final answer:
The second major weight equivalent in the metric system after the kilogram is the gram, where one gram is 1/1000th of a kilogram.
Step-by-step explanation:
The second major weight equivalent in the metric system, after the kilogram (kg), is the gram (g). While kilograms are the standard unit for heavier masses, grams are used for smaller weights, with one gram being precisely defined as 1/1000th of a kilogram (10-3 kg). It's important to note that in the metric system, weight is sometimes used interchangeably with mass, even though technically, weight is the force exerted by gravity on an object. The weight of an object is calculated by multiplying its mass by the gravitational acceleration, which is approximately 9.8 m/s2 (or for simplicity in calculation, often rounded to 10 m/s2).