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.

2 answers

both if they are measuring speed RELATIVE to them.
Julia rides her bike 10 km north with a constant speed of 12 kph and another 15 km north with a constant speed of 12 kph.

How long does the trip take?
What is her average speed?
What is her average velocity?