Question

I am unable to understanding about all the laws of Newton's motion please help me in understanding all the three laws of Newton's
Plz help me I am beginner in Physics Plz Help me!

Answer 1

Question#24918

I am unable to understand about all the laws of Newton's motion please help me in understanding all the three laws of Newton's Plz help me I am beginner in Physics Plz Help me!

Answer:

Newton's laws of motion:

1. First law:

The first law states that if the net force (the vector sum of all forces acting on an object) is zero, then the velocity of the object is constant. Velocity is a vector quantity which expresses both the object's speed and the direction of its motion; therefore, the statement that the object's velocity is constant is a statement that both its speed and the direction of its motion are constant.

Consequently,

- An object that is at rest will stay at rest unless an unbalanced force acts upon it.

- An object that is in motion will not change its velocity unless an unbalanced force acts upon it. This is known as uniform motion.

Examples:

A body on the spring

The net force is equal to zero.

A car on the road moving with the constant speed on the direct line

The net force is equal to zero.

2. Second law: The acceleration $\mathbf{a}$ of a body is parallel and directly proportional to the net force $\mathbf{F}$ acting on the body, is in the direction of the net force, and is inversely proportional to the mass $m$ of the body, i.e., $\mathbf{F} = m\mathbf{a}$ .

The second law states that the net force on an object is equal to the acceleration product on weight of the body.

Moving an object an inclined plane

P - is the weight of the object

N - is the normal force

F - is the net force (the vector sum of N and P)

An object moving with acceleration $a = F / m$ , were $m$ is the mass of the object.

3. Third law: When a first body exerts a force $\mathbf{F}_1$ on a second body, the second body simultaneously exerts a force $\mathbf{F}_2 = -\mathbf{F}_1$ on the first body. This means that $\mathbf{F}_1$ and $\mathbf{F}_2$ are equal in magnitude and opposite in direction.

The third law states that all forces exist in pairs: if one object $A$ exerts a force $\mathbf{F}_A$ on a second object $B$ , then $B$ simultaneously exerts a force $\mathbf{F}_B$ on $A$ , and the two forces are equal and opposite: $\mathbf{F}_A = -\mathbf{F}_B$ . The third law means that all forces are interactions between different bodies, and thus that there is no such thing as a unidirectional force or a force that acts on only one body. This law is sometimes referred to as the action-reaction law, with $\mathbf{F}_A$ called the "action" and $\mathbf{F}_B$ the "reaction". The action and the reaction are simultaneous, and it does not matter which is called the action and which is called reaction; both forces are part of a single interaction, and neither force exists without the other.

At the first example (a body on the spring)

A body exerts a force $\mathrm{P}$ on a spring.

A spring exerts a force $\mathrm{F}$ on a body.

Two force $\mathrm{P}$ and $\mathrm{F}$ are equal and opposite.