Solutions to Physics Simplified and Brought to You by Extramarks

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LAWS OF MOTION ICSE Class 9
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Contact and Non-Contact Forces

•  Force is defined as an agent which changes or
  tends to change the state of rest or uniform
  motion of a body or changes its direction or
  shape. The SI unit of force is newton (N). In cgs
  system, force is measured in dyne.  Force is the
  cause of motion of a stationary body, stopping,
  decreasing or increasing the speed of a body and
  change in the shape or size of a body. Force is
  further dived as Contact force Contact force is
  defined as the force between two bodies when they
  are in physical contact. Non-contact force
  Non-contact force is defined as the force between
  two bodies when they are not in physical contact.

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First Law of Motion

• Newtons first law of motion is also known as law
  of inertia. Inertia of a body is defined as the
  tendency of the body to resist any change in its
  state of rest or motion. Mass is the measure of
  inertia of a body.Newtons first law of motion
  states that every body resists a change in its
  state of rest or of uniform motion in a straight
  line unless acted upon by an external force.
  Inertia of three typesInertia of rest It is
  the inability of a body to change its state of
  rest by itself.Inertia of motion It is the
  inability of a body to change its state of motion
  by itself.Inertia of direction It is the
  inability of a body to change its state of
  direction by itself.

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Second Law of Motion

•  Newtons second law states that the rate of
  change of linear momentum of the body is directly
  proportional to the force applied on it and the
  change takes place in the direction of the
  applied force. In all the given examples,
  momentum is reduced thereby reducing the effect
  of force.

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Third Law of Motion

•    Newtons third law of motion states that for
  every action there is an equal and opposite
  reaction. Examples of Newtons third law of
  motion are walking, recoil of gun and rocket
  propulsion.  Action and reaction forces always
  react on the different bodies. A man leaving a
  boat and a boy hitting a wall are also examples
  of Newtons third law of motion.

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Extramarks Approach

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• https//www.extramarks.com/study-material/icse-cla
  ss-9/physics-laws-of-motion

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