Question

Which law is the special case of Newton's second law of motion?
A.Newton’s third law
B.Kepler’s law
C.Newton’s first law
D.Coulomb’s law

Answer 1

Hint: From Newton’s First Law of Motion we know that unless an outside force acts on it, a body at rest will remain at rest and a body in motion at a constant velocity will remain in motion in a straight line unless an external force acts upon it.


Complete step-by-step solution:
Here,
We know that,
Newton's First Law of Motion states that unless an outside force acts on it, a body at rest will remain at rest and a body in motion at a constant velocity will remain in motion in a straight line unless an external force acts upon it.
If a body is undergoing an acceleration (or deceleration) or a change of motion direction, an external force must act upon it. Outside forces are often referred to as net forces or des-equilibrium forces.
The property that a body has is called inertia, which, if optional, prevents motion if it is at rest, or avoids speeding or slowing down. Inertia is proportional to a body's mass, or the amount of matter that a body comprises. The more mass a body possesses, the more inertia it has.
The Second Law of Motion states that if an unbalanced force acts on a body, the body will undergo acceleration (or deceleration), that is, a velocity shift. A body at rest is known to have zero velocity, (a fixed velocity), one might say. So, an unbalanced force is any force that causes a body to move. Also, an unbalanced force is any force, such as friction or gravity that causes a body to slow down or speed up.
This law can be shown by the following formula \[F = ma\] where
\[F\] is the unbalanced force
\[m\] is the object's mass
\[a\] is the acceleration that the force cause
Hence,
The correct answer is (C) which is Newton’s first law.

Note: Newton's laws refer to objects that are idealised as single point masses, disregarding the size and form of the body of the object to focus more easily on its motion.
This can be done if the object is small compared to the distances involved in its analysis, or the deformation and rotation of the body is insignificant. And a planet may thus be idealised as a particle to study its orbital motion around a star.