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I Collision of two bodies

  1. Apr 2, 2017 #1
    During a collision between a truck and a wall, an occupant of the truck is thrown forward because of inertia; he continues moving forward. Why does the occupant stop eventually? What is the resultant force that opposes his forward motion? Is this force the equal and opposite normal reaction force of the wall on the car? How does the occupant experience this force even though there is no direct contact? (not to be sadistic or anything)
     
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  3. Apr 2, 2017 #2

    davenn

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    HI Marcus
    welcome to PF :smile:

    is this homework ??
    if so, you should have posted in the homework section using the template

    regardless of if it is or isn't .... lets have some effort by you to answer your questions
    Here on PF we like to help people learn by thinking for themselves

    Dave
     
  4. Apr 2, 2017 #3
    No. It isn't homework. Yes. I have thought about it which is why you see more than 1 question. I'm asking for confirmation.
     
  5. Apr 2, 2017 #4

    jbriggs444

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    What forces can you think of that the occupant does experience?
     
  6. Apr 2, 2017 #5
    Normal reaction force which originally is the normal force of the wall on the car. How does the occupant experience this force since he eventually comes to a stop?
     
  7. Apr 2, 2017 #6

    Nidum

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    Clue : What is the purpose of seat belts and air bags ? What happens when these safety devices are not fitted ?
     
  8. Apr 2, 2017 #7

    A.T.

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    If this is really so hard to imagine, just go on youtube and watch some crash test videos with dummies.
     
  9. Apr 2, 2017 #8
    @A.T. It's not hard to imagine. But WHY(hope you see those capitalized letters) do they stop eventually? @Nidum I know seat belts are there to stop eventually. But without seatbelts, will the occupant still stop? Or will he keep on going until he bangs into the windowscreen
     
  10. Apr 2, 2017 #9

    Nidum

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    That's it - most commonly the driver hits the windscreen and/or the steering wheel . Can't say it always happens this way though .
     
  11. Apr 2, 2017 #10
    @Nidum so there is no normal force of the wall on the car acting on the occupant
     
  12. Apr 2, 2017 #11

    jbriggs444

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    The force of the wall on the car acts on the car. Hence the phrase "on the car".
     
  13. Apr 2, 2017 #12

    A.T.

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    http://bfy.tw/B01B
     
  14. Apr 2, 2017 #13

    davenn

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    have a GOOD THINK about it ( hope you see the capitals :wink: )
    you give a ball that is sitting on the ground a push/kick .... it will eventually stop
    now what forces do you think there are acting on the ball to cause that to happen ?
     
  15. Apr 2, 2017 #14

    davenn

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    Gosh, surely you can answer that one yourself
     
  16. Apr 3, 2017 #15

    Nidum

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    Before the crash the victim has the same forward velocity as the vehicle . When the vehicle is brought to a rapid stop the driver initially still has this velocity and carries on moving in the original forward direction . Driver finally gets stopped by whatever is the first non moving object he contacts .
     
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