*Average speed

Speed between two instants is called average. Mathematically it is measured as the total distance covered per unit time spent. It is scalar & always positive.

i.e. Average speed

1. For a given time interval average velocity is single valued while average speed can have values depending upon path followed.
2. Average velocity & average speed are equal only for motion along a straight line with no reversal.
3. The average speed can never be – ve or zero while average velocity can be.
4.  If a particle travels distances x₁ , x₂ & x₃ with speeds v₁ , v₂ & v₃  during time intervals t₁, t₂ & t₃ respectively, then its average speed is    If x₁  = x₂  = x₃, then this relation becomes harmonic mean of individual speeds.                                                                                                                                                                      Also if t₁ = t₂ = t₃, then the average speed is be given by Arithmetic mean of individual speeds.