Newtons Second Law - What is Newtons 2nd Law of Motion - [Examples]

At the end of the article, you will be able to describe- What is Newtons Second Law -Definition, measurement of the 2nd law of motion, examples of newtons 2nd law. Let's start discussing one by one.

Newtons 2nd Law of Motion

This fact was first recognized by Newton who expressed it as his second law of motion.

A Clue to the second law of motion - Suppose a fixed force is applied on the two bodies of different masses for the same duration. The lighter body gains a higher speed than the heavier one. However, the change in momentum in both cases is found to be the same. This shows that the same force for the same time causes the same change in momentum for bodies of different masses.

Must Read: What is Momentum in simple terms?

Just now I introduced momentum right. Why did I introduce momentum? it is because momentum played a role in Newton's second law of motion. In second law of motion, Newton basically told that there exists a relationship between force and moving them right.

What is Newtons Second Law - Definition

It states that the rate of change of momentum of a body is directly proportional to the external force applied to the body and the change takes place in the direction of the applied force.

This law can be divided into two parts:

The rate of change of momentum is directly proportional to the applied force -  If you have a heavy stone and a very small stone. It is very obvious that heavier objects require more force than the smaller to move. So, greater the mass greater is the force required to make it in to start its motion.

The larger the force acting on a body, greater is the change in its momentum.

Since the change in momentum is equal to the product of mass and the change in velocity and the mass of the body remains constant, so the rate of change of momentum is directly proportional to the rate of change of velocity i.e., acceleration. Hence, force F is proportional to both mass (m) and acceleration (a).
F = m x a
Where,
'F' is the force applied to the object.
'm' is the mass of the object. Unit of mass is kilograms (kg).
'a' is the acceleration of the object.

The change of momentum occurs in the direction of the force - If a body is at rest, a force will set it in motion. If a body is moving with a certain velocity, a force will increase or decrease this velocity accordingly as the force acts in its same or opposite direction.

Measurement of Newtons Second Law

The mathematical representation of Newton's second law of motion is the force is directly proportional to:

In other words,

                                                     

Examples of Newtons 2nd Law

You can also plot the graphical representation of Newton's second law of motion. The three graphs are shown here give the relationship between force, mass, and acceleration when one of these quantities is kept constant.
 

• 1 N = 1 kg m/s²
• 1 Kg = 1000 g
• 1 meter = 100 cm
• 1 Newton = 1000 g x 100 cm/s²
• 1 Newton = 10⁵ g cm/s²
• 1g cm/s² = 1dyne
• 1N = 10⁵ dyne

Newtons Second Law Examples

Let's move on to Newton's second law examples. As we know from the first law that to overcome the inertia of an object. We have to apply unbalanced force. 

Newton's second law talks about how fast an object would move. 

In mathematical terms, Newton's second law states that force is the product of mass and acceleration to cause an object to accelerate or speed up. 
A force must be applied. The more force you apply the quicker you accelerate.

Question - If we have two swings. If you apply the same force on both swings. Who's goes faster?   The swing with the little kid goes very high. Pushing fat man sitting on the swing with the same force does not go far. It is because it has more mass than the little kid. So, the more mass there is the force required to push the object is also greater.

Let's look at the mathematical formula of the second law again. It's the product of mass and acceleration. We've already learned that if there's more mass in an object to move it we need more force.

Now, the kid sitting on the swing. If we apply little force then it goes a small distance. Now, if we apply a lot more force. It goes very high. So, to get more acceleration. We need to apply higher force.

So, now you can understand the relationships among force mass and acceleration. 
This is all about the basics of What is Newtons Second Law -Definition, measurement of the 2nd law of motion, examples of newtons 2nd law.