1. Why Do Objects Move or Stay Still?
In our daily life, we see some objects moving while others stay still. A rolling ball eventually stops, but a book on a table remains at rest until someone pushes it. To understand why this happens, we study the laws of motion.
These laws help us explain every kind of motion—from a falling fruit to a launching rocket.
1.1. Motion Needs a Cause
Objects do not start moving on their own. Something has to push or pull them. This ‘something’ is called a force. The same way, objects do not stop moving suddenly unless a force acts on them.
1.2. Rest and Motion Depend on Forces
If forces acting on an object balance each other, the object stays at rest or keeps moving at the same speed. If they become unbalanced, the motion changes.
2. What Are the Laws of Motion?
The laws of motion are three simple rules that describe how objects behave when forces act on them. These laws were given by Sir Isaac Newton and are the foundation of all classical physics.
2.1. Newton’s Three Laws
- First Law: Objects tend to stay in their present state unless a force changes it.
- Second Law: Force, mass and acceleration are related.
- Third Law: For every action, there is an equal and opposite reaction.
2.2. Why These Laws Are Important
These laws help us understand everyday events like walking, driving, lifting, kicking a ball, and jumping. They also explain advanced concepts like rocket motion and collisions.
3. Before Newton’s Laws: Common Observations
Even before learning the mathematical laws, we can understand basic ideas about forces through simple observations.
3.1. Objects Need a Push or Pull
You cannot move a heavy table without pushing it. You cannot stop a fast-moving ball without applying force. This shows motion changes only when forces act.
3.2. Objects Resist Changes in Motion
A passenger in a bus moves forward when the bus suddenly stops, and moves backward when the bus starts suddenly. This happens because the body resists changes in motion. This idea leads to the concept of inertia.
4. Setting the Foundation for Newton’s Laws
To properly understand Newton’s laws of motion, we first need to understand a few basic terms like force, inertia, mass, momentum and acceleration. These ideas help us see how objects start moving, stop moving, or change their speed and direction.
4.1. The Role of Force
Force is the reason behind any change in motion. A force can make an object speed up, slow down, start moving, stop moving, or change its direction.
4.2. The Role of Inertia
Inertia is the natural tendency of all objects to resist changes in their state of motion. This idea becomes the heart of Newton’s first law.
4.3. How the Three Laws Work Together
Newton’s laws are connected:
- The first law describes inertia.
- The second law explains how force changes motion mathematically.
- The third law explains interactions between objects.