Linear Motion

• Linear motion means movement in a straight line.
• • Distance is how much ground an object has covered during its motion.
  • It is a scalar quantity.
  • S.I. unit of distance is metres.
• • Displacement is the distance covered by an object in a specific direction.
  • It is a vector quantity
  • S.I. unit of displacement is metres.
• • Scalar quantity are quantities with size but no direction.
  • For example: distance, speed, time, temperature, mass, volume, density.
• • Vector quantities are quantities with both size and direction.
  • For example: displacement, velocity, acceleration, force, momentum, pressure.
• • Speed is the distance travelled per unit time.
  • S.I units are: Mass- Kilogram (kg)
  • distance- metre (m)
  • time- seconds (s)$Speed=$$distance/time$
• • Velocity is the rate of change of displacement per unit time.
  • S.I unit is metres per sec (M/s)$Velocity=$$displacement/time$
• Average speed is the total distance travelled divided by the total time taken.$Average speed=$$total distance/total time$
• Instantaneous speed is the speed of a moving object at a given time.
• Acceleration is the rate of change of velocity with time.$Average speed=$$total distance/total time$

  $accel=$$Final velocity- Initial velocity/ time taken$ (a= v-u/t)

  where: v= Final velocity

  u= initial velocity

  t= time taken
• • Deceleration means an object is slowing down is used velocity is greater than the final velocity.
  • Decelerating objects have negative acceleration.
• Characsteristics of Distance-time graphs:

  • Graph is a straight line- it is moving with a constant speed.
  • Graph is a curve. It's gradient is increasing with time- the body is accelerating.
  • Graph is a curve. It's gradient is decreasing with time- body is decreasing.
  • Graph is horizontal (parallel to x-axis)- distance is not changing. This means body is not moving, it is stationary.