Relative vectors - how do you determine?

[Trooper100]

1. The problem statement

I find it sometimes difficult to come up with the equation relevant to the question. If anyone has any tips, your help is appreciated.

2. Relevant example

For example:

A passenger climbs aboard a northbound bus and walks toward the back at a rate of 1.8m/s. The bus starts off up the street at 9.2m/s. What velocity will the passenger appear to be walking relative to:

A) a person who is walking 2.1 m/s south along the sidewalk
B) a person who is walking 2.1 m/s north along the sidewalk

The Attempt at a Solution

Let p = passenger in the bus
b = Bus
g = guy who is walking

My attempt: a) Vpg = Vpb + Vbg is this correct? why or why not? thanks.

 

[tiny-tim]

Hi Trooper100!

(try using the X₂ tag just above the Reply box )

Let p = passenger in the bus
b = Bus
g = guy who is walking

My attempt: a) Vpg = Vpb + Vbg is this correct? why or why not? thanks.

Yes, that's correct, because you've put the letters in the right order … pg = pb + bg.

(For example , if you wanted to know V_pb,

you would write V_pb = V_pg + V_gb = V_pg - V_bg )