(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Okay, I've been set a piece of coursework to compare the reaction times of catching a ruler, with, or without a certain variable. (I've chosen either eye.)

I'm having trouble working out the exact amount of time it takes the person to catch the ruler. (Yeah, I have attempted it. :) )

2. Relevant equations

(Explained in section 3.)

3. The attempt at a solution

The ruler weighs 0.025kg.

I hold the ruler at 1.04m. (An average of 10 times holding the ruler at a neutral position)

To calculate the gravitational potential energy I do:

0.025 x 1.04 x 10

This gives me = 0.26 (Joules)

The ruler falls 12 cm, (the person caught it at 18cm)

So 0.025 x 0.12 x 10 = the kinetic energy = 0.03

The formula for speed is :

Speed squared = kinetic energy/(0.5 times the weight)

0.03 divided by 0.0125 = 2.4

The square root of 2.4 = 1.549193338

To two decimal places = 1.55m/s

And if the ruler travelled 12 cm at 1.55m/s

0.12/1.55 = 0.0774 seconds……

I must have gone wrong somewhere...because I swear its 'physically' (pun intended) impossible for them to catch it that quickly?

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# Homework Help: Speed of catching a falling ruler

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