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Car flipping over another car

  1. Dec 24, 2013 #1
    Hi gurus

    I am not physics but I would like to know the following

    car A jeep Grand C
    car B Jeep Liberty

    is it possible for car A to flip over car B if A hit B at 45-50 MPH. in a dry road condition ?
    Thanks a bunch
     
  2. jcsd
  3. Dec 24, 2013 #2

    mfb

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    I don't know the size of those cars (and I think it is your task to give them) and a proper answer would probably require a detailed study how the collision happens, but the kinetic energy is certainly sufficient. B is stationary before the collision?
     
  4. Dec 24, 2013 #3
    mfb

    Thanks a bunch for your reply , I know all the information was very general but I just wanted to know if it was possible for that scenario to happen.

    car A
    LENGTH 15ft 6.7in
    WIDTH 7ft 0.2in
    HEIGHT 5ft 9.4in
    GROUND CLEARANCE 0ft 8.5in

    Car B

    LENGTH 14ft 6.4in
    WIDTH 5ft 11.6in
    HEIGHT 5ft 11.9in
    GROUND CLEARANCE 0ft 8in

    B was moving, turning left when A hit it.

    Thanks again for all your time and help on this.
     
  5. Dec 24, 2013 #4

    mfb

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    With a ramp, the car could reach a height of 20m (~60 feet), so if one car can somehow act similar to a ramp...
     
  6. Dec 24, 2013 #5

    AlephZero

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    As mfb said there is plenty of energy to do it. Call the speed 64 ft/sec which is a bit less than 45 mph. If something suddenly made the car move vertically upwards, it would take 2 seconds to reach its highest point, against a gravitational acceleration of 32 ft/sec^2, and would reach a height of 64 feet above the ground.

    So the only "problem" is finding a way to create enough force to change the car's momentum from horizontal to vertical. Most likely, doing that would use the car's KE bend the bodywork, not propel it vertically upwards.
     
  7. Dec 25, 2013 #6
    Ale/mfb

    I by no means are a tech guy, so when you mean ramp and vertical, i get lost very fast, car a is going 45-50 mph when car b crossed in front of car a on a street with a small downslop (is a two lane street) that is how car A hit car B on the driver side, so at this point ,can car A flip car b once. is it possible , just to hit a car with the above specs and make one car rollover?

    it seems like 45-50 mph is not that fast, but what do I know, you guru know this better.

    Thanks again a bunch am happy holidays
     
    Last edited: Dec 25, 2013
  8. Dec 25, 2013 #7

    AlephZero

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    Ah.... lLanguage fail, maybe. When your first post said "flip over" I read that as "car A goes over the top of car B". I think mfb went down the same path. FWIW neither of us have American English as our first language!

    So we got thinking about "how high would a car get, if it drove onto a ramp looking something like a ski jump, at 45-50 mph..."

    Now you say "rollover" - that seems quite possible. i once saw a car doing about 40 mph roll over just by hitting the curb, (= British English kerb) going round a curve that was meant for speeds more like 20mph than 40mph.. So I guess a collision between two cars could have the same result.
     
  9. Dec 26, 2013 #8
    Ale.

    my bad for not explaining myself much better, this is time you use to help others and me.. us who seek help should be more explicit on our posts.

    again thanks a bunchhhhh for all your help and time,

    is juts like it seems like not too much speed for car A to hit car B on the driver side and make car Bto rollover.

    so it is possible for a car going 45-50 mph to make another car rollover ?
     
    Last edited: Dec 26, 2013
  10. Dec 26, 2013 #9

    jbriggs444

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    Yes, definitely possible.

    You are suggesting that it seems like there is not enough energy available? In order to get
    a car to roll over, it only takes enough energy to lift the car from its starting position on all four wheels to a position where the center of gravity is balanced directly over two wheels. This only requires raising the center of gravity by about two feet. [If you assume that the CG starts about 2 feet off the ground and 3.5 feet inside the tires then it ends at √(22+3.52) ~= 4 feet off the ground for a net increase of 2 feet]

    As calculated up-thread, the energy in a 45 mph car is enough to lift that car about 60 feet off the ground.

    As a rule of thumb, with an inelastic collision between two objects of cars equal rigidity and mass, one of which begins at rest, half of the initial kinetic energy will be dissipated in crumpled steel and half will remain as the kinetic energy of the two wrecks (before they slide to a stop). So that leaves you with about 30 feet worth of kinetic energy.

    Half of this energy is in the car doing the hitting. Half of this is with the car that was hit. So that leaves you with about 15 feet worth of kinetic energy in the car that was hit.

    You only needed 2 feet worth of kinetic energy for a rollover. So you have at least seven times what is needed. The only real question is whether the impact angle and dynamics are such that the target's tires "bite" and hold while the target rolls instead of slipping so that the target slides. My opinion is that collisions are sufficiently messy that both possibilities exist.
     
  11. Dec 26, 2013 #10
    Thanks to all for your post and help, and the following I mean in the most respectfully way, " its insane how you gurus come up with this calculation and facts" I just tried to to understand the vertical and horizontal part of this threat and had to get botox for the headache I got.

    Thanks to all of you and wish you a happy holidays
     
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