Brainstorm: System Schemas
Constant
Non-Constant
How do forces affect people standing?
Force Diagrams
Constant Velocity
When the velocity is constant, the forces are balanced. Therefore when the train is moving with a constant veocity, you will not reel backwards.
Non- Constant Velocity
When the velocity isn't constant, the forces are not balanced. The force of the pole will try to keep you in your place; push or pull you forward if you reel backwards.
Presentation by: Tenzin Ngawang and Sabrina Stewart-McDonald
Why do we stumble backwards when the train accelerates?
one
Person
Person
two
Floor
(cc) photo by Metro Centric on Flickr
(cc) photo by jimmyharris on Flickr
Pole
Earth
(cc) photo by Metro Centric on Flickr
Person
Floor of the train
Earth
So?
How can we stop ourselves from reeling backwards when the train accelerates?
If you can, take a seat.
Try to position yourself so that the pole is slightly behind you; stopping you from reeling backwards.
The Broad Street Line
The Earth
The Floor of the train
-prevents the person from floating away; it represents gravity. If this force weren't acting, the person would be stuck on the roof of the train instead of being on the floor.
Person standing on the train
If possible, you can lean against a wall that is in the opposite direction that train is traveling in.
-holds the person up; prevents the person from falling. If this force weren't acting, the person wouldn't actually be on the train.
The Pole
-helps the person pull themselves forward when they begin to stumble backwards. If this force were't acting, then people wouldn't have any way to stabilize themselves and could possibly fall over if the train continued to increase velocity.
Floor <--> Person
F
Floor <--> Person
F
Pole
F
Earth <--> Person
F
Earth <--> Person
F