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Force And Laws Of Motion

What you will learn

  • First law of motion: An object continues to be in a state of rest or of uniform motion along a straight line unless acted upon by an unbalanced force.

  • The natural tendency of objects to resist changes in their state of rest or of uniform motion is called inertia.

  • The mass of an object is a measure of its inertia. Its SI unit is kilogram (kg).

  • Force of friction always opposes motion of objects.

  • Second law of motion: The rate of change of momentum of an object is proportional to the applied unbalanced force in the direction of the force.

  • The SI unit of force is kg m s–2. This is also known as newton and represented by the symbol N. A force of one newton produces an acceleration of 1 m s–2 on an object of mass 1 kg.

  • The momentum of an object is the product of its mass and velocity and has the same direction as that of the velocity. Its SI unit is kg m s–1.

  • Third law of motion: To every action, there is an equal and opposite reaction and they act on two different bodies.

  • In an isolated system (where there is no external force), the total momentum remains conserved.