Weight transfer during hard braking?

Question

Weight transfer during hard braking?

Ferrarist (Automotive)

(OP)

2 Sep 17 11:01

Ok, have some confusing question about weight transfer while braking.
Let's say we have a car that weights 1000kg - front axle is 500, rear - 500.
If brakes and slicks are capable to produce great braking force, let's say 2G, will the TOTAL overall weight of the car during hard braking will ALWAYS be 1000kg?
For example if weights 1000kg, will during braking front axle support 800kg, while rear axle 300kg, giving total weight under hard braking 1100kg under all four wheels?
Is the total weight G-force related, or it's constant?

BrianPetersen (Mechanical) · Answer 1 · 2017-09-02 21:56:39

Go back to first year physics, and draw a free body diagram.

Unless the braking force is causing the car to uniformly accelerate upward, the force of gravity down and the force of the ground acting up on the tire contact patches (all of them added up) must be equal and opposite.

If there's a car in which slamming on the brakes causes the car to jump off the ground and leap over whatever the obstacle is in front of it, I haven't owned it. Would be a rather interesting feature ...

Ferrarist (Automotive) · Answer 2 · 2017-09-03 10:46:24

So, the sum of all weight supported by all 4 wheels in hard braking will always be same?

BrianPetersen (Mechanical) · Answer 3 · 2017-09-03 14:01:09

Again, draw your free body diagram.

F = m A has to be true in both horizontal and vertical motion components.

Looking at the vertical component, if the ground is level, and the vehicle is not taking off for the sky, then vertical acceleration A = 0, it's irrelevant what the mass is, and F (the sum of ALL forces acting upon the vehicle in the vertical direction) must therefore be ... answer it yourself.

This is first year physics ... high school physics back when I took it.

Tmoose (Mechanical) · Answer 4 · 2017-09-03 15:30:05

Not braking, but.......
I'm grateful SUVs have made the 3 dimensional time dependent aspect of "weight transfer" into a daily occurrence.
https://www.youtube.com/watch?v=ocjZwAh_QKY

A few decades past it took a fuel altered to play trix with physix.
Nanook was one of the best,
"Nanook T-bucket fuel altered AA/FA, all up in the air over something."
https://i.pinimg.com/originals/b9/c9/1e/b9c91ef0d6...

JayMaechtlen (Industrial) · Answer 5 · 2017-11-11 06:21:58

Love the Nanook pic - notice the throttle blades are closed!
Obviously the vertical acceleration was non-zero at some point.

Jay Maechtlen
http://www.laserpubs.com/techcomm

gruntguru (Mechanical) · Answer 6 · 2017-11-14 23:02:40

Chuckle. Well, we know the vertical acceleration was 1g the entire time the car was out of contact with the ground!

je suis charlie

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Weight transfer during hard braking?