Invent Your Own Speed Units !
         Why always use miles or kilometers per hour for speed ?

        
                 Dangle a weight -- Check it out !
                 But you need a string about 45cms..

        
         Don't have a Speedometer ! - No Problem
         Use the formula to calculate the speed you are travelling..

        
                 Does your School bus has a Tachometer ?
                 Check out - What a Tachometer does?....