A physical quantity with both a magnitude and a direction is referred to as force. The ‘direction of force’ is the direction in which it is applied. A force is defined as a pull or a push on a body. The three laws of motion outlined in Isaac Newton’s Principia Mathematica are frequently used to demonstrate the concept of force. When you apply force to something, it changes its condition of motion or rest. 

Applying force to an item can affect its velocity and direction. Furthermore, force has the capacity to alter an object’s shape. Newton’s laws of motion may seem self-evident today, yet they were revolutionary hundreds of years ago.

When objects are fixed, moving, or subjected to forces, the three laws of motion explain how they act. Let’s take a closer look at force and motion rules, as well as some key topics.

Force

The pushing or pulling of an object is referred to as force. Objects interacting with one another create push and pull. In physics, force is defined as:

“The force exerted on a massed object that causes it to change velocity”.

A spring balance can be used to calculate force, and the SI unit for force is Newton.

Newton’s Law of Motion

Sir Isaac Newton proposed three laws of motion to describe the link between an object’s motion and the force acting on it. Newton’s laws of motion are these three laws of motion. The law of inertia is another name for Newton’s first law. 

The relationship between applied force and the rate of change of momentum is described by Newton’s second law. The law of action and reaction is another name for Newton’s third law.

Newton’s First Law

Things can’t start, stop, or change direction on their own, according to Newton’s first law of motion. They need an external force to do so. The tendency of massive bodies to resist changes in their state of motion is known as inertia. Newton’s first law states that a body at rest or in uniform motion will remain at rest or in uniform motion until and unless it is subjected to a net external force.

The crucial thing to understand is that if there is no net force acting on an object as a result of uneven forces, the object will maintain its velocity. The item is considered to be at rest if its velocity is zero.

Newton’s Second Law of Motion

The relationship between force and acceleration is the subject of Newton’s second law of motion. The second law of motion is that

The acceleration of an item caused by a net force is proportional to its magnitude, in the same direction as the net force, and inversely proportional to the mass of the object.

The force applied is proportional to the rate of change in an object’s momentum. Newton’s second law of motion, as a result, can be expressed as follows:

Assume that a mass of m is moving in a straight line with a velocity of u. It is uniformly accelerated to velocity, v, for the entire duration, t, by applying a constant force, F.

The initial and ultimate momentums of the item are  p1 = mu  and  p2 = mv, respectively. Newton’s second law of motion can now be used to express a change in momentum:

f∝dpdt 

f∝mv-mut  

f∝mv-ut 

f∝ma 

f=kma 

k is known as proportionality Constant.

Newton’s Third Law of Motion

Statement: To every action, there is an equal and opposite Reaction.

When one body exerts a force on another, the second body simultaneously exerts an equal and opposite force on the first body. These two forces (action and reaction) are constantly acting on two different bodies at the same time. 

When we use a hammer to secure a nail to a surface, for example, the hammer exerts force on the nail. At the same moment, the hammer will be subjected to the same force as the nail. These two forces have the same magnitude but move in different directions.

Applications of Newton’s Law of Motion

Application of Newton’s First Law of Motion

• When a stack of books is placed on cardboard, it does not tumble when the cardboard is jerked out because the books on the cardboard struggle to maintain their inertia of rest.
• Due to the inertia of motion, the driver of a moving car leans forward when it comes to a quick stop. The driver’s lower body comes to a halt as soon as it makes contact with the vehicle, but his upper body continues to move.

Application of Newton’s Second Law of Motion

• While collecting a cricket ball, a fielder gently draws his hands backwards to extend the time during which the high velocity of moving balls decreases to zero. The ball’s acceleration is reduced, and the fielder’s hands are spared injury.
• When we put greater effort to the pedals of a bicycle, it accelerates faster.

Application of Newton’s Third Law of Motion

• A bird flying through the sky uses its wings to push the air downward. The air gives the bird a lift since it exerts an equal and upward force.
• When swimming in a pond, a person pushes the water backwards and downwards. At the same time, the water pushes the person forward, allowing him to float and swim in the water.

Conclusion

We can conclude from Newton’s law of motion that unless a non-zero force acts on an object, it will remain in its condition of rest or motion. 

The acceleration of an object is directly proportional to the force applied to it. When one body exerts a force on another, the other body will respond with a force of equal size but in the opposite direction.