Speed, displacement, velocity+ acceleration

• Speed is the distance travelled per unit time

  Speed= distance/time

  $Sp=$$d/t$
• The units of speed are m/s or km/h
• Displacement is the distance in a given direction
• Velocity is speed in a given direction

  20m/s due north, 50km/h 46°east
• Examples

  1.If a person runs 400m in 44 secs, what is the average speed?

  Distance: 400m

  Time: 44 secs

  Sp= d/t

  = 400m/44s

  = 9.091m/s

  2.a person has a speed of 6m/s. How long does it take them to cover 600m?

  Distance: 600m

  Speed:6m/s

  T= D/sp

  = 600/6

  = 100s
• Acceleration is the rate of change of velocity/speed

  Acceleration= change in velocity/time

  Acc= sp2-sp1/ t
• The unit of acceleration in m/s/s or m/s²
• Examples

  1. A runner accelerates from 9m/s to rest in 2 secs at the end of a race, what is her rate of acceleration?

  Spd1=9m/s

  Sp2= 0m/s

  Time= 2 second

  Acceleration= sp2-sp1/t

  =0-9/2

  =-9/2

  =-4.5m/s²
• Momentum depends on both mass and velocity

  Momentum= mass x velocity
• Examples

  A pea of mass 1g is traveling at a speed of 200m/s what is its momentum

  Mass= 1g

  Velocity= 200m/s

  Momentum= 1 x 200

  =200gm/s