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Classical mechanics - hunter and monkey - frame of reference

  1. Sep 20, 2015 #1

    This might sound very basic and but i am just starting to learn physics.
    I an lecture by prof. walter lewin, he descibes the hunter and monkey scenario. The monkey jumps from the tree as soon as the hunter aims and shoot his gun. the bullet hits the monkey anyway.
    In calculating the time it takes the bullet to hit the monkey, he calculates from monkey's frame of reference and class's frame of reference to be same. He also states that the time is same irrespective of a moving frame (monkey's) and static frame (Class).

    My doubt is, the monkey is accelerating with respect to the class. So the time and speed of bullet should not be the same for both as one is accelerating. From what i understand, an accelerating frame of reference will not produce same results as relative velocities will differ.
    Please let me know your thoughts on this. Am i missing something?

  2. jcsd
  3. Sep 20, 2015 #2


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    What happens cannot depend on the frame of reference, whether accelerating or not. The monkey is either hit or not.

    In Newtonian mechanics, time is invariant between different frames and so the time must also be the same in all reference frames. (This is different in relativity, but monkeys are not that fast.)
  4. Sep 20, 2015 #3
    Hi Orodruin,

    Thank you for the explanation. I tried measuring the time taken when the 2 are only along the vertical and it does work out. So as i understand the presence of gravity only alters the path of the objects. As such the time taken is the same else the monkey does not get hit.

    I think i understand. the non inertial frame concept affects the newton's laws as seen in the non inertial frame of reference. The behavior will not conform to the laws.
    So in newtonian mechanics, both frames measure the time at the same rate but the cause / effect will not make sense. We cannot predict the behavior correctly.
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