If you hit somebody laying down on the road, would slowing down actually do more damage? I was thinking this for the longest time. As you get slower and slower you have more energy towards the ground (weight of the car) whereas going fast you have less energy downwards.
The general theory of relatively says that the faster you are going the more mass you have so slowing down puts less energy normal force into the ground.
>>14822183
>As you get slower and slower you have more energy towards the ground (weight of the car) whereas going fast you have less energy downwards.
This is not how physics works.
At all.
>>14822183
depends
if you're going really fast and have incredibly low spring rates, you might not even do any damage
If youre going fast enough you can go trough matter
People are getting dumber each day
>>14822496
While oversimplified, he's essentially right though.
Think of gravity as a constant downward kenetic energy. With a constant mass, the more kenetic energy an object has moving forward, the less it has moving downward.
Same concept applies to fluids. Pressure drops with speed, this is how lift is created for aircraft.
>>14822183
yeah you are right
you should speed up if you are about to hit someone
better hitting them at 100mph than 5mph
>>14822584
yarp
>>14822789
>With a constant mass, the more kenetic energy an object has moving forward, the less it has moving downward
Not true in the least. Do the dropped bullet test for proof.
>>14822789
So the car is suddenly an ideal airfoil? That's fucking dumb.
What you want is to maximize the resultant vector (n + f) where n is the normal force and f is the forward force. It's not like hitting someone straight on isn't going to hurt them, and the person on the ground isn't 2 dimensional anyway. Fucking floor it.
>>14822789
No he isn't.
The weight of the car is constant. The downward component of force is always the same, regardless of what the horizontal component is.
The only difference that extra speed has is that you fucking hit the person with a much greater impact. If you end up rolling over them, they're still going to get just as crushed.
The only way that is going to change is if your car experiences aerodynamic lift as you speed up. In other words, if your car has aircraft wings or you drive a Merc CLK-GTR.
>>14822183
if you hit the brakes just right you might do more damage, but only if they're lying on the road and have enough clearance to go under the car
when you brake, your forward momentum gets transfered into both forward and downward force because of the suspension.
But only if you have enough speed and the car shifts weight to the front.
If you have enough speed and the right weight distribution you could transfer the whole weight of the vehicle on the front tires and do more damage to the person lying on the ground.
Jave we not heard of downforce? A car travelling at speed will have more downward force than a car moving slowly. Unless as other anon said your car has shit design and experiences lift at speed.
there is probably a threshold distance where everything before is less energy because you have had long enough to slow down to reduce energy and everything after is more energy on the initial impact due to more weight on the front
you should always slow down if their is a chance that the police will be involved, the consequences change depending on if you brake before or after impact
BRO, you asked all of these fucking /o/tists a physics question. They can barely wrap their mind around why hellaflushing their car is a bad idea.
Top kek.
>>14823959
>The weight of the car is constant.
Wrong. More weight is supported by the rear wheels during acceleration, and during deceleration the weight shifts to the front wheels.
https://en.wikipedia.org/wiki/Weight_transfer
So ideally, to minimize damage when running someone over, you want to be accelerating as they go under the front wheels, and then decelerate when they go under the rear wheels.
>>14824075
You are right. But the actual vehicle weight is constant.
The difference is the dynamic loading on the vehicle results in a shift of the "effective" centre of gravity (not the same as the centre of mass), so the portion of the vehicle weight supported by each wheel changes with the dynamic force on the vehicle (ie during acceleration and deceleration, both linear and during cornering).
Also, I like your idea.
>>14824127
>But the actual vehicle weight is constant.
w = m * a
It's not.
>>14824141
It is as the vertical component of acceleration is always 9.81m/s/s horizontal acceleation is irrelivant.
>>14824075
>So ideally, to minimize damage when running someone over, you want to be accelerating as they go under the front wheels, and then decelerate when they go under the rear wheels.
You'd need nerves of steel to pull this off
>>14824161
When you brake, the rear of the car wants to stay in motion.
If there is a front break bias, the rear of the car will move faster than the front, resulting in a downward force due to the car shifting weight on the front tires.
This is why you don't full front break at high speed with a mountain bike.
>>14824075
I am really looking forwards to the day when an Anon is in court for manslaughter and puts this up as his defence
>>14824195
What you are describing is the reaction force at the wheels and dynamic loading, not the vehicle weight.
The movement of the dynamic load means the proportion of the weight supported by each wheel changes. This gives the feeling that the weight has shifted, which is what we mean when we talk about load transfer or a car going light over its front wheels.
But the actual magnitude of the weight does not change.
The effect you are talking about with brake bias is different. If you have front brake bias, the contact patch between the front wheel and the road acts as a pivot point, and the inertia force of the vehicle/bicycle acts through the centre of gravity (well above the road surface).
Thus, the inertia force acting through the centre of gravity creates a moment / torque, which acts to turn the bike around the pivot point (ie the front wheel) and throw you over the handlebars.
>>14824195
So much missunderstanding in one post, you must be a troll.
>>14824260
that's a nice couple paragraphs of memewords
Since I'm on /o/ I expected you to never have driven a car, but I hoped the bike example would've been enough.
Practically speaking,
1)
The only factor speed in the x,y plane (horizontal) would have would be if your speed were such that you could overcome gravity. Practically speaking, if this were the case, upon hitting the subject in question you would both die.
2)
Shifting the weight of the car using acceleration/braking is also impractical, because by the time you were to do so, you'd have already fucked the pedestrian. Not to mention the fact that the difference in speed b/w the tire and the person would further fuck them.
3)
If you are at all concerned with their health you would avoid the pedestrian.
>>14823959
>cars don't experience aerodynamic lift
What do you fucking think spoilers, lips, and other downforce-providing aerodynamic aids are for?
>>14824788
At any realistic speed? looks.
There's gotta be some optimization that determines the ideal point between the intersection of the lines that represent pain from "force of impact from the car" and the "time spent being crushed underneath the wheels". You obviously don't want to be going slow as shit because then it takes you like a full 3 seconds to roll over the person which means greater pressure being applied to internal organs for longer, but I feel like there's also a point where going too fast means you deliver an equally damaging impact to internal organs just from the translational velocity of the tire.
Lemme see if I can brainstorm a way to quantify this. The second part isn't hard; you just figure out the kinetic energy of a tire using Newton's law, but the slow rolling over a body might be a little more difficult. You need to determine the time spent on the body using the rotational velocity of the tire and the width of the body you're driving over then determine the pressure being applied at that specific wheel and then figure out the average force needed to permanently damaged various internal organs and calculate the pressure being applied to each one of them over the duration of your tire rolling on the body.
but that's probably not impossible to do, all things considered
>>14824017
Normal modern cars experience slight lift at highway speeds to help with tire wear.
>>14824260
This is assuming that lift does not exist at all and that you could go as fast as an F1 car in a corolla and it wouldn't take off.
>>14822183
>As you get slower and slower you have more force downwards
>whereas going fast you have less force downwards.
Anon, You have your spoiler on wrong...
