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Why do we lean towards left

  1. Apr 25, 2010 #1
    Why do we lean towards left when the bus moves along a curved road to right.
  2. jcsd
  3. Apr 25, 2010 #2


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    Because your body has a natural instinctive response to resist external forces to stay upright and keep the vision-plane level. When you go around a corner in a moving bus, your body's inertia tends to keep it going straight in accord with the Newton's first law. However, since you are inside the turning bus, it doesn't feel to you as if you are just going straight, it feels like you are being pulled toward the outside wall of the bus as it goes around the turn. This apparent "force" is what you are working against when you lean "into" the turn.
    Last edited: Apr 26, 2010
  4. Apr 26, 2010 #3
    According to the principle of equivalence gravity is indisdinguishable from acceleration. It means that inside a closed box you can not make an experiment that discerns gravity from acceleration.
    Since the acceleration is to the right, we might just think of it as being attracted by a pseudo force of gravity to the left.
  5. Apr 26, 2010 #4
  6. Apr 26, 2010 #5


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    You can also think of it as the vehicle is pushing you to the right via friction (from the seat) but not directly pushing yout head, so your upper body is kind of being swung around by your point of contact.
  7. Apr 26, 2010 #6
    You are reducing your velocity in your original direction as you transfer it to the new direction. When you lean to the left you are leaning in your original direction, same as when you press the brakes on your car and it pushes you forward.
  8. Apr 26, 2010 #7
    When the entire world moves to the right and you stay in place, to you, it seems that the world stayed in place and you moved to the left.
  9. Apr 28, 2010 #8
    What makes you think this is the absolute way to see the situation?
  10. Apr 28, 2010 #9
    The question is why do you feel a force when you accelerate. This is what you are doing when you are adding velocity to an orthogonal basis vector. The vehicle is changing it's relative velocity and so the seat grabs your bum and pulls you along with it. The fact that you feel a force in the opposite direction of acceleration agrees perfectly with the conservation of energy.
  11. Apr 28, 2010 #10
    To keep from falling over...
  12. Apr 28, 2010 #11
    You would need to lean to the right to keep from falling over.....
  13. Apr 28, 2010 #12
    I had to think about it, but you're right. If you leaned to the left, wouldn't you fall outta your seat?
  14. Apr 29, 2010 #13
    Yup, thats why when you are in a vehicle that accelerates too fast you might fall over.
  15. Apr 29, 2010 #14
    I didn't even think about that...so I guess the answer to the original question is, that you don't.
  16. Apr 29, 2010 #15
    Not always. Consider free fall under gravity. You don't feel any force.
    You will feel it, if its not a volume force(a beautiful term I saw in the Fundamentals Of Physics book by Resnick, Halliday).
  17. Apr 30, 2010 #16
    You are not accelerating in free fall however. You are only accelerating when you are on the ground.

    You always feel a force when you are accelerating. General Relativity 101.
  18. Apr 30, 2010 #17
    Because the little bubble in your inner ear shifts to the left and it tells your body to shift to the left to keep the bubble centered.
  19. Apr 30, 2010 #18
    Nah, test dummies also lean to the left.

    Helium balloons lean to the right, now there is food for thought.
    Last edited: Apr 30, 2010
  20. May 2, 2010 #19
    What? Care to explain what you have posted?
  21. May 3, 2010 #20
    You are not accelerating in free fall.

    The air around you is accelerating, because the air is touching the ground. The buildings around you are accelerating, because they are on the ground.

    When you are in a gravitational field you accelerate at the rate g in the direction opposite the mass. Where g is the gravitational acceleration, about 9.8 near earth.

    If you are in free fall you are falling with acceleration equal to the gravitational acceleration g in the direction of the mass. 9.8 - 9.8 = 0
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