Question

Which law of motion is also known as the Law of Acceleration?

• A. First
• B. Second
• C. Third
• D. Fourth

Hint:

Second law connects force and motion mathematically using \( F = ma \), making it the most practical law in problem-solving.

Answer 1

The Correct Option is B

To solve the question about which law of motion is known as the Law of Acceleration, we need to examine Newton's laws of motion. These laws are fundamental principles of classical mechanics and explain how objects move under the influence of forces. Let's analyze each option:

1. First Law of Motion: This law is also known as the Law of Inertia. It states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. This law is primarily concerned with the state of rest or uniform motion.
2. Second Law of Motion: This law is known as the Law of Acceleration. It states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. Mathematically, it can be expressed as F = ma, where F is the net force applied, m is the mass, and a is the acceleration produced. This equation shows that force causes changes in the motion of an object, making it the Law of Acceleration.
3. Third Law of Motion: This is known as the Law of Action and Reaction. It states that for every action, there is an equal and opposite reaction. This law deals with interactions between two bodies.
4. Fourth Law: There is no fourth law in Newton's original laws of motion.

Given the options, the correct answer is the Second law of motion because it specifically defines the relationship between force and acceleration, thus earning the name "Law of Acceleration."

Answer 2

A quick way to check which law deserves the name "Law of Acceleration" is to see which one actually contains acceleration in its defining equation, and to see what happens numerically when it is applied.

1. First: Also known as the Law of Inertia, its statement, that a body stays at rest or in uniform motion unless acted on by a force, contains no equation involving acceleration at all; it is a qualitative statement about resistance to change.
2. Second: Its defining equation is \( \vec{F} = m\vec{a} \), which explicitly solves for acceleration as \( a = \dfrac{F}{m} \). For example, a force of 10 N acting on a mass of 2 kg produces an acceleration of \( a = \dfrac{10}{2} = 5 \, \text{m/s}^2 \). Because the law's entire equation is built around calculating acceleration from force and mass, it is directly named the Law of Acceleration.
3. Third: Also called the Law of Action and Reaction, its equation form is simply \( F_{\text{action}} = -F_{\text{reaction}} \), which involves only forces between two bodies, with no acceleration term appearing anywhere.
4. Fourth: No such law exists in Newton's original three laws of motion.

Only the second law's formula directly produces a value for acceleration once force and mass are known, which is exactly why it carries the name Law of Acceleration.

Therefore, the correct answer is Second.