Newton's law of motion

Mechanics is a science which deals with the motion of objects, and it has a long history. Isaac Newton discovered the laws of motion based on mathematical theory in 300 years ago. To date, Newton's laws of motion are widely recognized as one of the most fundamental equations to learn mechanics. A brief explanation of Newton's laws of motion is described as follows;

First law: A law of inertia

The law of inertia is familiar with our daily life. Generally, a moving object keeps its velocity. For example, this means is that objects moving at a speed of 10 km/h continue to run at the same speed unless an external force is applied. On the other hand, the body at rest remains at rest unless an external force is applied. Although it is easy to understand the law of inertia for the stationary object comparing with the moving object. If you slide a block on the floor, it will slide to some distance and stop. Also if you are riding a bicycle, it will fell when you stop pedaling. At this time, both the block and the bicycle receive a force called friction from the floor and the ground. The movement stops because they receive friction force. If there is no friction, the blocks can slide to infinity, and the bicycle on a flat road could advance endless. (By the way, bicycles cannot proceed without friction). For example, air hockey game floats pucks from the floor with air to reduce the friction and create smooth movement.

Second law: A law of motion

This law is hard to understand unless you look at the equation. It is no exaggeration to say that this equation is the best-known equation in physics, which is called the equation of motion. It is shown as follows. \begin{equation} \vec{F} = m \vec{a} \end{equation} where \( \vec{F} \) and \( \vec{a} \) applied force and acceleration in the same direction. From this point, when the force \( \vec{F} \) applied, the object is accelerated in the same direction as \( \vec{F} \) with acceleration \( \vec{a} \). Further, by solving the equation of motion for \( \vec{a} \), the following equation obtained. \begin{equation} \vec{a} = \frac{\vec{F}}{m} \end{equation} The magnitude of the acceleration increases in proportion with applied force \( \vec{F} \). Also, it is inversely proportional to the mass \( m \) of the object. It must be noted that the more object gets heavier, the more force needs to accelerate the object. Such a phenomenon is more likely to see in everyday life. If you want to move a heavy object, the more quickly to move, the more power has need. Similarly, a light stone is easier to move more than a heavy stone.

Third law: A law of action and reaction

The law of action and reaction may be difficult to imagine. Even if you push against a wall, you won't be stuck in the wall. At this time, both the wall and yourself are remaining stationary. In other words, the magnitude of force which you push the wall and which the wall pushes you back are balanced. The force on the wall is called action, and the force on your object is called reaction. The law in which both forces are balanced is called the law of action and reaction. The forces between action and reaction are equal in magnitude and opposite in direction.