posted by ganga .
you walk up the aisle in a bus moving 10m/sec and a seated friend you are walking 1.5m/sec. another friend who just got off the bus standing there waving at you says you are moving 11.5m/sec.and the stalker friend riding his bike next to the bus say your speed is 0m/sec. which friend is right.
both if they are measuring speed RELATIVE to them.