matticus
Guru
This is utterly unsupported by the physics of the situation. <end>
UK SUV Petition
- Thread starter sheddy
- Start date
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This is utterly unsupported by the physics of the situation. <end>
BoldonLad
Not part of the Elite
- Location
- South Tyneside
If you say so, and, I am sure you are correct, according to my O level Physics knowledge, but, in practical terms, I am not sure what the odds are on a pedestrian or cyclist surviving a collision with a 1 tonne vehicle travelling at (say) 40mph, versus a 3 tonne vehicle travelling at 40mph. In the latter case, you may be more mangled, but, dead is dead, there aren’t degrees of deadness, to the best of my knowledge.
Jody
Stubborn git
Doubt 100kg is going to make much difference to the kenetic energy of either vehicle
matticus
Guru
Good. That's a start. Let's read on ...
Two issues here:
- collisions do happen below 40 mph too. I was hit by a driver accelerating from a stand-still a few metres away from me (exact speed unknown). Are you going to ignore all those? Was your choice of the number 40 by any chance a debating tactic?
- Yes of course peds/cyclists sometimes survive such collisions. Partly because they're often glancing blows.
Got any more insight for us?
BoldonLad
Not part of the Elite
- Location
- South Tyneside
My point was rather that in either case, the kinetic energy is quite enough to kill a pedestrian or cyclist. The “surplus” is of not real consequence if one is dead. A bit like arguing about being killed by a 303 bullet, or a shell from a tank, either way, you are dead.
Jody
Stubborn git
I'm in total agreement. The weight of a car is irrelevant to a pedestrian collision.
matticus
Guru
Really? A Fiat 500 weighs about 900kg. At 30mph colliding with a pedestrian it will impart 12070 newtons of energy on average impact, with a peak impact force of 24140 Newtons (allowing for a 1 second impact duration). It takes 2300 newtons of energy to crush a human skull.
In contrast, an ID4 weighs 1891kg. At 30mph colliding with a pedestrian it will impart 17000 newtons of energy on average impact, with a peak impact force of 34012 newtons.
In both cases the pedestrian is likely to be dead. However, the ID4 is equipped with cameras, auto collision avoidance and lane keeping. As soon as it detects the pedestrian it slams on the brakes faster than the human driver can react. It also warns the driver way before the collision with audible alarms and flashing red lights.
The Fiat isn't.
There are a lot of factors involved about the way the collision happened, and how momentum was removed from the pedestrian. If you are lucky, you survive. The mass of the vehicle is not a factor, its the way that energy is imparted and removed. A gradual slow down is more likely to give a positive outcome.Apparently not - I am not typing this from the grave
Jody
Stubborn git
Apparently not - I am not typing this from the grave
Probably due to only having a few meters worth of acceleration?
Alex321
Guru
- Location
- South Wales
Any clues as to why you believe that?
Alex321
Guru
- Location
- South Wales
It doesn't matter what the speed is, the simple fact is that for any give speed and angle, once the difference in weight between the two colliding objects is enough that the momentum of the larger object is not measurably affected by the collision, it doesn't matter how much heavier than that the larger object is.
And in any collision between a normal sized motor vehicle and a pedestrian, that point has been well passed.
Whether it hits you ate 20mph, 40mph or 60mph will make a difference as to how likely it is to kill you, as will the angle of impact, but the weight of the vehicle will not alter that likelihood unless the vehicle is so light that hitting you will make a noticeable difference to the momentum of the vehicle.
Profpointy
Legendary Member
Not really. Being against excessively heavy vehicles that are more damaging to pedestrians and cyclists doesn't seem an unjust singling out. Fair enough farmers having them as work vehicles, but for city use by those who never go off road or tow is antisocial as it harms others
Profpointy
Legendary Member
A 1000kg will make a considerable difference.
My own car is excessively heavy at a tonne-three quarters - nearly double the weight of a modest 60s or 70s car. Twice the momentum and KE. Many of these 4x4 luxury vehicles are another tonne again
Jody
Stubborn git
Not against a pedestrian it won't. A 1 tonne car is still going to accelerate the person at almost an identical velocity as a 3 tonne car. Given both cars are the same proportions and travelling at the same speed, without braking. The momentum of the vehicle is not going to be affected in any meaningful way.
