## Note on Newton’s Laws of Motion

• Note
• Things to remember

In this chapter, we will study about the case of the motion due to force. Force is the central problem in mechanics. From day to day life experience we define force as push or pull. One of the effects of the force is to produce motion to a rest body or to bring at rest to a moving body. A force can cause both the translation as well as rotational as well as rotational motion on an object.

#### Newton’s Laws of Motion

Newton’s First Law of Motion

According to first law, a body at rest remains at rest or moves with constant speed on a straight line if no external force acts on it.

Inertia of Rest

The opposition of a body to change its state of rest is called inertia of rest.

Examples:

1. When a bus suddenly moves, the passenger falls backward. It is because the lower part of the body of the passenger tends to fall backward.
2. When we shake a mango tree, the mangoes fall down. It is because when we shake the tree, the mango tend to be rest due to inertia where as the branches are in motion. That is why the mangoes tend to be at rest due to inertia where as the branches are in the motion. That is why the mangoes get detached from the branches.
3. When we hit a carpet with a stick, the dust particles come out of it. By hitting the carpet it is set in motion where as the dust particles remain at rest.

Inertia of Motion

The opposition of a body to change its state of motion is called the inertia of motion.

Examples:

1. When we jump from a running bus, we fall forward. It is because the foot comes to the rest but our upper part is still in motion due to inertia and we fall forward.
2. When the brake of the bus is suddenly applied , we tend to fall forward . It is because the lower part in contact to the bus comes to rest where as the upper part is still in motion. So we fall forward.
3. An athlete runs a certain distance before taking a long jump . It is because the velocity of the athlete in air is to the velocity at the time of jump and covers a long distance.

A force can cause both the translation as well as rotational as well as rotational motion on an object.

According to this law, everybody in this universe continues in its state of rest or of uniform motion in a straight line unless it is compelled by some external force to change the state.

The opposition of a body to change its state of rest is called inertia of rest.

The opposition of a body to change its state of motion is called the inertia of motion.

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