Question

The SI unit of weight is:
A. Kg
B. Newton
C. Pounds
D. Tonne

Answer 1

Hint: We know that weight of a body is the force working on the thing because of gravity. And its SI is that of force that is the newton. Then we see that Kg is the SI unit of mass. After that, we see that tonne and pound are also units of mass that are \[1tonne = 1000Kg\] and $1pound(lb) = 0.4359Kg$.

Complete Step-by-Step solution:
In engineering and science, the weight of a body is the force working on the thing because of gravity. The unit of measurement for weight is that of force, which in the international system of Units (SI) is that the newton. Generally, the term "weight" is usually used in place of mass, and therefore the verb "to weigh" means "to have a mass of" or "to measure the mass of". The kilogram is the SI unit for the mass as it is the measure of the quantity of matter that a body holds. For instance, a body with a mass of 1 kilogram will be weighing nearly 9.8 newtons on the surface of the earth, and the same body will have about one-sixth of the weight on the earth when it is on the surface of the Moon.
Tonne is the unit of mass that is \[1tonne = 1000Kg\] and $1pound(lb) = 0.4359Kg$. So option A is correct.

Additional information:
Sometimes weight is defined as a vector quantity, that is the gravity working on the body and sometimes it is also defined as a scalar quantity that is the magnitude of the gravity. Some define it as the magnitude of the opposite force developed on a body by mechanisms that hold it in place. The weight of a body is measured by a spring balance. Therefore, during a state of free fall, the weight becomes zero. In this sense, terrestrial objects that are present on the surface of the earth are often weightless neglecting the air resistance.
Even though mass and weight are two completely different quantities, these two terms are often confused with one another.
$weight = mass \times acceleration$

Note: For these types of questions we need to remember the difference between mass and weight that is $weight = mass \times acceleration$. Then we need to know that weight is measured in Newton N (SI unit) and pound-force (lbf) whereas mass is measured in kg (SI unit), tonne, pound (lb), and an ounce.