Question

Physical independence of force is consequence of
A. First law of the motion
B. Second law of the motion
C. Third law of the motion
D. All of these laws

Answer 1

Hint: We can do vector addition of forces and forces can be resolved into their components. One force does not influence another. Force is a vector quantity i.e., having both magnitude and direction.

Complete answer step by step:
The physical independence principle:
It states that the effect of a force on a body is not affected by the presence of other forces. So even if there are a number of forces acting on the same body, each force has its own influence as other forces were absent.
This is the characteristic feature of force. It helps us to solve any complex problem (where a large number of forces are acting) by resolving each force into horizontal and vertical components since force acting in vertical direction will be independent of force acting in horizontal direction. For example a projectile motion can be viewed as a combination of horizontal and vertical motion.

First law of Motion:
It states that “Everybody continues its state of rest or state of uniform motion unless and until external unbalanced force acts on it.”
So when a body is at rest or is moving with uniform velocity net force acting on it is zero. When an unbalanced force acts on it, the body moves in the direction of force. Thus the effect of this unbalanced force is not influenced by the presence of other forces. This implies that forces act independently of each other and they have no influence on others.
In order to calculate net effect we do vector addition of all forces because each force has its own direction.
Answer is A. First law of the motion

Additional Information:
Second law of the motion:
The rate of change of momentum is directly proportional to the force applied to it and it is in the direction of applied force.
Third law of the motion:
Every action has an equal and opposite reaction.

Note: Any force can be resolved into two independent components, vertical and horizontal components. In reverse, any two forces can be combined to form a resultant component. This is because of physical independence of forces which is a direct consequence of the first law of motion.