Article: Biker nabbed at 234km/h

[agentrfr]

You're looking at the kinetic energy, not the handling. A Golf's handling at 80kph is far worse than a bike's at 200kph.

Ja sure, I totally agree 100% that its easier to avoid obstacles on a bike than in a car - butI'm analysing the situation when there is a crash, not the chances of a crash happening.

The biggest problem also see from this, is that you get these mindless adrenaline junkies that use their bikes for their fixes. They start having so many of these "close calls", and it over inflates their ego, and they keep pushing the envelope further and further.

Once you start high-way speeds, you are literally piloting a missile. You only have to stuff up once to kill not only youself, but anyone that you accidently hit too.

Then these lamb steaks go twice the high way speed. The innocent people they inevatibly hit have pretty much 0% chance of survival.

 

[noxibox]

Once you start high-way speeds, you are literally piloting a missile. You only have to stuff up once to kill not only youself, but anyone that you accidently hit too.

Then these lamb steaks go twice the high way speed. The innocent people they inevatibly hit have pretty much 0% chance of survival.

Well that's the thing, can we have some statistics on how many other people speeding bikers kill. I'm curious to know how often it happens.

Shouldn't the maximum speed of vehicles be based on their mass?

 

[Garson007]

Shouldn't the maximum speed of vehicles be based on their mass?

The problem there is that breaking distance is (theoretically) only dependent on speed, so no. However, yes lots of trucks have upper limits that are lower than the road limit.

 

[McSack]

Well that's the thing, can we have some statistics on how many other people speeding bikers kill. I'm curious to know how often it happens.

?

Anecdotal, but from what I notice from fallen bikers threads in one or two forums (fora?), the people in the car(dare I say cagers without getting my head bitten off ) tend to walk away with minor injuries, if any and the biker is FUBAR'd

 

[Rkootknir]

The problem there is that breaking distance is (theoretically) only dependent on speed, so no. However, yes lots of trucks have upper limits that are lower than the road limit.

Not quite - mass is definitely a contributing factor, but you're right that speed is more important. A simple rule is that, all other factors remaining the same, going at 2x a certain speed will require 4x the stopping the distance. So if you can come to a dead stop in 20m from 60km/h it will take at least 80m to come to stop from 120km/h.

 

[Garson007]

Not quite - mass is definitely a contributing factor, but you're right that speed is more important. A simple rule is that, all other factors remaining the same, going at 2x a certain speed will require 4x the stopping the distance. So if you can come to a dead stop in 20m from 60km/h it will take at least 80m to come to stop from 120km/h.

Mass shouldn't contribute if you make a single overly simple assumption - a constant friction coefficient. Reality is obviously different. What you say is true as well, of course.

 

[scotty777]

Um no.

This is where an easy mistake can be made. Kinetic energy depends A LOT more on speed than it does mass. A citi golf has a gross laden mass of 1270 kg (http://www.um.co.za/specifications/volkswagen_citi_golf_1_4i_velociti_(2006).aspx)

So for a golf at 80km/hr

Ek = 0.5*1270*(80/3.6)^2

= 313 580.25 J

That bike had 422 500 J of kinetic energy.

That bike has 34.73 % more kinetic energy than the car, even though the bike is 1/6th the mass.

And this is ignoring the fact that cars have crumple zones to absorb most (70%) of this energy.

Granted, a bike has better brakes and is more manouverable (at low speeds), but if you are sitting on a missile, be it pointy or big and flat - either one is going to kill people.

A pointy hard missile is much more deadly than one that is a squishy in the front.

Momentum is directly proportional to the rigid bodies mass and velocity,

namely:
p = mv

So, the bike @234km/h, and @ 200kg has a momentum of:

13000kgm/s.

The truck @ 40km/h and @ 5 tonnes has a momentum of:

55555.6kgm/s

Finally, the citi golf @80km/h and @ 1270 kg:

28222.2kgm/s


Thus, we can see that the bike doesn't have enough momentum behind it to stop the truck... (I think energy is a really bad way to calculate this because energy IS NOT CONSERVED)

It's like shorting a charged capacitor with an uncharged one... Energy will got be conserved because there is a large flow of it, through a medium with loses... In this case
the truck and bike will likely waste energy on loud noises, bending metal etc...


If the bike hit the golf head-on, and the golf was going 40km/h, then both objects would probably stop...