Question

Which of the following is a measure of the gravitational force acting on an object?
A) Mass
B) Weight
C) Pressure
D) None of these

Answer 1

To attempt this question you should be familiar with the term gravitational force. Gravitational force is a force that attracts any two objects with mass. We also call gravitational force an attractive force because it always pulls masses together. And mass is the measure of the amount of matter in a body while weight is the measure of the amount of force acting on a mass.

Complete solution:
Step 1: Option A is mass. And mass is defined as the amount of matter in a body. It has nothing to do with gravity when we talk about the amount of matter. If you measure some amount of mass on earth, say, 5 kg then it will not change on the surface of the moon. We cannot calculate the gravitational force if we know the amount of matter only. Consider another example, if a fish has the same density as water has then the fish will not experience gravitational force but the fish still has mass. Therefore mass is not a measure of the gravitational force.

Step 2: Option B is Weight. Let us define the weight first. Weight is the measure of the amount of force acting on a mass due to the acceleration caused by gravity. Consider an example here, when you stand on a weighing machine, the machine tells how much force the earth is pulling towards its center. Here, the gravitational force acting upon you by the earth is measured in weight. If you will stand on a weighing machine on the surface of the moon the weight will change. In other words the gravitational force on you by the moon will be different. The formula for gravitational force is ${F_g} = mg$ , where ${F_g}$ is the force caused by gravity of the earth, $m$ is the mass of the body and $g$ is the acceleration due to gravity of the earth. Therefore the weight is the measure of the gravitational force

Step 3: Option C is pressure. Pressure is defined as the force divided by the area perpendicular to the force over which the force is applied. The formula for the pressure is $P = \dfrac{F}{A}$ . We can see in the formula that the pressure is not affected by the gravity caused by the earth. Therefore pressure is not a measure of the gravitational force.

Hence the correct option is option B.

Note: Mass and Weight both are very similar terms. To avoid confusion between mass and weight remember the following difference.

Weight:	Mass:
It depends on the gravity. More gravity means more weight and less gravity means less weight.	It doesn’t depend on gravity. It is the same everywhere.
It can be zero if gravity is zero.	It cannot be zero.
It is a vector quantity.	It is a scalar quantity.
It's S.I. The unit is Newton.	It's S.I. unit is kg.