I am currently working on an assignment for my physics class, but I believe my question is biology related.

For a two person lab, I am trying to time how long it takes a tennis ball to fall two meters, Using basic physics equations I was able to determine that the ball should take around 0.66 seconds to hit the ground but my results are generally very off.

Would I be able to react faster if I were to stop the timer when I felt the ball hit my other hand, or would I have a worse reaction time than if I were to use my current method of stopping the timer when I see/hear the ball hit the ground.

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    $\begingroup$ Try them both and see what works better. Why bother asking here? $\endgroup$
    – MattDMo
    Commented Oct 12, 2016 at 19:23
  • $\begingroup$ Averaging them both would work, but technically speaking I want to know what would work. I am at home and I have no access to the materials . $\endgroup$ Commented Oct 12, 2016 at 19:24
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    $\begingroup$ Pretty certain it is touch. As far as I know the sensations of haptic feedback can create a motor reaction without requiring any higher-order cognitive processing, meaning that they'll take the monosynaptic route. On the other hand, the visual processing takes longer, because in this case, higher order cognitive processing is required. $\endgroup$
    – Ebbinghaus
    Commented Oct 12, 2016 at 20:23
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    $\begingroup$ Are far as experimental design goes, you'd have to take into account that the person stopping the timer is probably predicting when it will hit the ground. They'd be looking at the movement of the ball in the few centimetres before it actually hits the two-metre mark. Similarly, you'd have to determine how to start the timer. Do they start after they notice the ball being dropped, or do you do a similarly-predictive countdown (e.g. "1, 2, 3, drop"). $\endgroup$
    – Sparhawk
    Commented Oct 13, 2016 at 0:16
  • $\begingroup$ I can't say what I would do, but I would try very hard to find a non-biological "trick" to measure the time lapse. This may be the purpose of the exercise (or it may just be to try to physically see that the equation works). Just to give you some idea of what is humanly possible, scientists have a "trick" (used at the LIGO observatories) that allows measurement of a change in length (of a 4 mile laser beam) of less than the diameter of the nucleus of an atom). By the way, I agree .. TOUCH. $\endgroup$ Commented Oct 22, 2016 at 15:00

1 Answer 1


A "touch" or "haptic" sensation will be much faster due to several reasons:

  • Haptic feedback can be processed without the presence of any higher-order cognitive processing, therefore meaning that the signals are being processed via a monosynaptic route.
  • There are short reflex arcs between the spinal cord and the limb (meaning that you can react before you are consciously aware of it)

A visual sensation will be much slower:

  • The processing of the signal will require higher-order cognitive processing, and this takes time. I read that it takes between 50ms-200ms. (polysynaptic route)

Interesting article about this topic

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    $\begingroup$ but does it practically make any difference for an experiment like this? $\endgroup$
    – user17915
    Commented Oct 13, 2016 at 1:21

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