Class 11th science physics(laws of motion)

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What is Inertia?

The property of an object by virtue of which it cannot change its state of uniform motion along a straight line or rest on its own is called as inertia.It is the measure of the mass of a body. There are 3 types of inertia.
  • Inertia of rest
  • Inertia of motion
  • Inertia of direction

What is Force?

A force is a push or pull upon an object resulting from the object’s interaction with another object.Force can be categorized into two types;
  • Constant Force
  • Action at a distance force

What are Newton’s Laws of Motion?

  1. First Law:“A body continues in its state of rest or of uniform motion in a straight line unless it is compelled by some external force to change that state.”
  2. Second Law:“The rate of change of momentum of a body is directly proportional to the impressed force and takes place in the direction of the force.”
  3. Third Law:“To every action, there is an equal and opposite reaction.”Important Questions
  1. Aristotle’s view that a force is necessary to keep a body in uniform motion is wrong. A force is necessary for the practice to counter the opposing force of friction.
  1. Galileo extrapolated simple observations on motion of bodies on inclined planes, and arrived at the law of inertia. Newton’s first law of motion is the same law rephrased thus: “Everybody continues to be in its state of rest or of uniform motion in a straight line unless compelled by some external force to act otherwise”. In simple terms, the First Law is “If the external force on a body is zero, its acceleration is zero”.
  1. Momentum (p ) of a body is the product of its mass (m) and velocity (v) :p = mv
  2. The laws of motion help us understand the behaviour of objects when they are moving, standing still and their behaviour when forces act upon them. There are three laws of motion. Here in this article, we have provided a brief description of each of the laws clearly.

    Newton’s Law of Motion

    Sir Isaac Newton was an English mathematician, astronomer and physicist who gave three laws which proved to be fundamental laws for describing the motion of a body. These are generally known as Newton’s laws of motion. We will discuss each law of motion one by one in detail.

    Newton’s First Law of Motion:

    Newton's First Law
    Newton first law of motion states that “A body at rest or uniform motion will continue to be at rest or uniform motion until and unless a net external force acts on it”. Suppose a block is kept on the floor, it will remain at rest until we apply some external force to it. Also, we know that it takes us more effort or force to move a heavy mass. This is directly related to a property known as Inertia. This law is also known as the law of inertia.

    Newton’s Second Law of Motion:

    The first law has already given us a qualitative definition of force. Now we are interested in finding out its magnitude. According to newton's second law of motion, the net force experienced by a body is directly proportional to the rate of change of momentum of the body. It can be written as:
    Newton's Second Law
    f∝dPdt⇒f∝mv−mut⇒f∝m(v−u)t⇒f∝ma⇒f=kma
    Where k is the constant of proportionality and it comes out to be 1 when the values are taken in SI unit. Hence the final expression will be,
    F = ma


Newton’s Third Law of Motion:

Newton's Third Law
According to newton's third law of motionl, for every action, there is an equal and opposite reaction. Forces are always found in pairs. For instance, when you sit on a chair, your body exerts a force downward and that chair needs to exert an equal force upward or else the chair will collapse.

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