Just finished my first Physics exam, Bus braking Problem

[rexexdesign]

Homework Statement

I just took the test, but I can't remember the question word for word, it was along these lines though: You are standing on bus. It suddenly brakes what is the force that makes you lean forward?
A: Kinetic friction of your shoes on the bus floor
B: Static friction of your shoes on the bus floor
C: The normal force of the bus floor on you
D: No Force

Homework Equations

Concept question

The Attempt at a Solution

I was thinking B or C, I finally chose B, because wouldn't the normal force still be directed upward? I eliminated A, because my feet are not moving, but the static friction is holding me in place, yet I am leaning forward.

Any thoughts?

Thank you

 

[sandy.bridge]

Yes, I would go with static friction. I would assume the "falling foreward" is present because initially there is a decelleration due to the bus stopping, and hence a force is developed by the person on the bus to oppose this. Once the bus is fully stopped, this force may lag behind and hence push one foreward.

 

[rexexdesign]

Yes, I would go with static friction. I would assume the "falling foreward" is present because initially there is a decelleration due to the bus stopping, and hence a force is developed by the person on the bus to oppose this. Once the bus is fully stopped, this force may lag behind and hence push one foreward.

Thank you for your insight! The test was hard, but fair, I can't wait to get the results.