Describing Motion

Describing Motion

1. Speed

   • average speed = distance/time
     • v=x/t
   • Units of Speed
     • metres per second
     • centimetres per second
     • kilometres per second
     • kilometres per hour
     • miles per hour

2. Distance and Displacement, Scalar and Vector

   • In Physics, we are often concerened more wih the distance moved by an object in a particular direction rather than its total distance
     • This is called its Displacement
       • Displacement is a VECTOR
         • As it has a magnitude but also a direction
     • Distance is a SCALAR
       • As it has magnitude but no direction
         • The complete distance travelled(in this case)
     • Velocity is is the rate of change of displacement
       • velocity=change in displacement/time taken

3. Displacement against Time Graphs

   • From t0 to t1 the object is travelling at constant velocity, from the start to x1
   • The rate of change of displacement is not constant, so the object is accelerating
   • From t1 to t2 the object is stationary
   • From t2 to t3 the object is travelling at a constant velocity back to the start

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