How fast am i going?

  • Thread starter laytonsdad
  • Start date
  • #1

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?

Thank you for your time.
 

Answers and Replies

  • #2
UltrafastPED
Science Advisor
Gold Member
1,912
216
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.
 
  • #3
Doc Al
Mentor
44,912
1,169
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.)

Short answer: You are correct.
 
  • Like
Likes 1 person
  • #4
Thank you for the fast response(s).
 
Last edited:
  • #5
CompuChip
Science Advisor
Homework Helper
4,302
47
Man I hope we didn't ruin the atmosphere at home for you :-)
 
  • #6
867
60
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.
 
  • #7
phinds
Science Advisor
Insights Author
Gold Member
2019 Award
16,089
6,079
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 :smile:
 
  • #8
CompuChip
Science Advisor
Homework Helper
4,302
47
If we are nitpicking, how much is 77 miles per hour - 8.46 . 10-9 inch? Can I eat that?
 

Related Threads on How fast am i going?

  • Last Post
Replies
5
Views
3K
  • Last Post
Replies
5
Views
5K
  • Last Post
Replies
3
Views
4K
Replies
15
Views
3K
Replies
6
Views
765
Replies
4
Views
569
Replies
4
Views
2K
  • Last Post
Replies
23
Views
10K
  • Last Post
Replies
8
Views
7K
  • Last Post
Replies
12
Views
3K
Top