Friday, January 19, 2007

Physics/Mathematics Question need your help...

Ok, yesterday 蘋果日報 Headline was a traffic accident on the 青衣北橋 Tsing Yi North Bridge.

The report was that a truck had a minor accident first and collided with a barrier. One of the passengers got off and checked the damage. Then they chose to flee the scene.

About after 800m of driving, they struck the lane partition and got killed in a second accident.

Now... The truck supposedly was travelling at 140 km/h when it struck the partition the second time that led to the fatal mistake.

Now my question is... One of these trucks not carrying cargo, could they accelerate to 140km/h from a standing start with 800m?

I would appreciate it greatly if someone out there can answer me. What would the acceleration be? (I have long given back nearly all my differentiation back to my calculus teacher) 0 - nearly 100mph in 800m... Is it possible?


  1. Secondary school physics:
    Square(Final Velocity) - Square(Initial Velocity)
    = 2 x Acceleration x Distance
    Final Velocity = 140kph = 39m/s
    Initial Velocity = 0
    Distance = 800m
    => Acceleration = 39x39/2/800 = 0.95m/s/s
    Compare with Gravitation Force 地心吸力 9.8m/s/s
    I am not sure whether trucks possess power of one tenth of G-Force or not.

  2. I know a Ferrari's acceleration is 0.98g

    So maybe 0.1g is doable by truck of that size without cargo.

    Thanks! Yes, I remember that formula now from my days of mechanical mathematics.

  3. Actually that was spot on. According to the following webpage from US Dept of Transportation, a typical semi-trailer truck would have acceleration of 3ft/s/s, which roughly equals to 0.91m/s/s

  4. There is indeed talent everywhere in our little SAR...

    Talent everywhere... US Dept of Transportation... I didn't even know they did statistical research into this... great!


  5. a=(V2-U2)/2S
    代入 V=140000/3600 U=0 S=800
    貨車30秒 也不是沒有可能