Weight transfer & Braking.-

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Caito
Caito
13
Joined: 16 Jun 2009, 05:30
Location: Switzerland

Weight transfer & Braking.-

Post

As I was re-reading the Physics of Racing (which I recommend, http://phors.locost7.info/ ) a doubt appeared, which I know is quite stupid and, anyway, I can't solve it.
Reading part 1 (weight transfer) I came across this drawing
Image

As I see things, looking at the pic if we imagine the car moving forward, wheels would spin CCW(counter clockwise)
If we wanted to stop the car and hit the brakes ( this car had disc brakes :p), this would create a torque going in the CW direction, exerting a force in a forward direction to the floor, the floor reacting with a force in the opposite direction, making the car brake (as in the pic).

The thing is, wouldn't that brakeforce generate (as seen in the pic) generate CCW torque wich would make the wheel spins faster. This (I know) is a total contradiction, because we were braking the car.

For some reason I can't see where my reasoning is failing, hopefully some of you would guide me to reason :)


Thanks a lot, and.. sorry for this question but I had this urging on my mind.
Come back 747, we miss you!!

The_Man
The_Man
0
Joined: 15 Mar 2009, 11:59
Location: Mumbai India

Re: Weight transfer & Braking.-

Post

Newton's Third law: you are getting that bit wrong.
Draw FBD of the wheels separately that might help.

You need CCW torque to counter the braking force. If the braking force did the braking for you why would you need brakes?
IIT Bombay Racing
Vehicle Dynamics FSAE 08; FS 09