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• Rectilinear motion or linear motion: It is a motion in a straight line.
• Magnitude: Numerical value of any physical quantity [E.g. of Physical quantities: displacement, force, etc].
• Scalar quantity:
  • Quantity having magnitude but not direction.
  • Examples: Time, Mass, Distance, Speed, etc
• Vector quantity:
  • Quantity having magnitude as well as direction.
  • Examples: Acceleration, Velocity, Displacement, etc.
• Displacement: Shortest distance between initial and final position of object. SI unit: meter (m). If initial and final position are same, magnitude of displacement is zero.

  Click here to watch video on Rectilinear Motion, Uniform Motion and Non Uniform Motion

• Uniform motion: Object moves same distance in equal time interval. E.g: A car covers the distance of 2 km in every 5 minutes.
• Non uniform motion: Object covers different distance in same time interval. E.g: Motion of car in crowd, bouncing of ball, etc.
• Speed: Distance travelled by an object per unit time. SI unit: m/s
• Velocity: Speed of an object in a specific direction. SI unit: m/s
• Comparison between Speed and Velocity:
  

  Speed	Velocity
  Distance travelled per unit time	Speed of object in specific direction
  It is a scalar quantity	It is a vector quantity
  Average speed(v): Total distance travelled(s) / Total time (t)	Average velocity (vav): (Initial velocity(u) + Final velocity(v) ) / 2
  SI unit: m/s	SI unit: m/s

• Acceleration:
  • Change in velocity of an object per unit time.
  • Positive acceleration: Acceleration in direction of velocity
  • Negative acceleration: acceleration opposite to direction of velocity.
  • SI unit: m/s²
• Comparison between Velocity and Acceleration:
  

  Velocity	Acceleration
  Speed of an object in a specific direction	Change in velocity of an object with respect to time
  It is a vector quantity	It is a vector quantity
  Formula: Velocity (vav) = (u+v) / 2	Formula: Acceleration (a) = (v-u) / t
  SI unit: m/s	SI unit: m/s2

  	Uniform	Nonuniform
  Velocity	Direction and speed of object is constant with respect to time	Direction or speed, or direction and speed is variable with respect to time
  Acceleration	Velocity of an object increases or decreases with respect to time	Random increase or decrease in velocity with respect to time

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• Position – Time Graph or Distance – Time graph:
  • Represents change in position of an object with respect to time.
  • For uniform motion: Straight line graph (linear graph)
  • For non uniform motion: Non linear graph
  • For object at rest: Straight line graph parallel to x axis
  • Using graph, velocity can be calculated by formula: v = (s₂-s₁) / (t₂-t₁)

  

• Velocity – Time Graph:
  • Represents change in velocity of an object with respect to time
  • For uniform motion: Straight line graph parallel to x axis. Area enclosed in the graph gives magnitude of displacement.
  • For uniformly accelerated motion: Linear graph. Area enclosed in the graph gives distance travelled by an object.
  • For non uniformly accelerated motion: Non linear graph showing different shapes.

  

• Velocity time graph can be used to derive equation of motion
  • v = u + at
  • s = ut + ½ at²
  • v² = u² + 2as
• Uniform circular motion: Motion of object long circular path with constant speed. Object continuous to perform circular motion due to centripetal force acting on object from centre of circular path. If centripetal force breaks, circular motion is disturbed and object moves along the tangential path.
  Click here to watch video on Equations of Motion and Uniform Circular Motion