# How fast am i going?

## Main Question or Discussion Point

My wife and I have had a debate going for some time now.

If I am on a bus going 65 mph and I run tword the front of the bus at 12 mph, at that point how fast am I traveling
I say that I am traveling at 77 mph and she says I am traveling at 65 mph. Who is correct?

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UltrafastPED
Gold Member
You are correct ... until you bump into the front of the bus.

You can verify this by noting that a car driving 77 mph (your wife can be the driver) passing the bus will be appear stationary for you.

This is Galileo's relativity in action.

Doc Al
Mentor
I say that I am traveling at 77 mph and she says I am traveling at 65 mph. Who is correct?
How fast you are traveling only makes sense if you specify how fast relative to what. Relative to the road, you'd be traveling at 77 mph. Relative to the bus, you'd be traveling at 12 mph. Not sure what your wife had in mind with 65 mph. (Relative to someone running alongside the bus at 12 mph, you'd be traveling at 65 mph.)

1 person
Thank you for the fast response(s).

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CompuChip
Homework Helper
Man I hope we didn't ruin the atmosphere at home for you :-)

Neither, though you are much closer then she is. Your true speed is about 8.46 billionths of an inch less then 77 miles per hour, due to relativistic effects.

phinds
Gold Member
2019 Award
Neither, though you are much closer then she is. Your true speed is about 8.46 billionths of an inch less then 77 miles per hour, due to relativistic effects.
Nitpicker

CompuChip