# Reaction Time Ruler Test

Here is a simple reaction time test using only a ruler, and a little bit of calculating. This is a good science class project. This test uses the known properties of gravity to determine how long it takes a person to respond to the dropping of an object by measuring how far the object can falls before being caught. An even simpler test, a variation of this test but not involving any calculations, requires making your own Reaction Timer. There are some commercially available variations of this test - see this review of Reaction Sticks.

• purpose: to measure reaction time, hand-eye quickness and attentiveness.
• equipment required: 1 meter long ruler or Yardstick, calculator
• procedure: The person to be tested stands or sits near the edge of a table, resting their elbow on the table so that their wrist extends over the side. The assessor holds the ruler vertically in the air between the subject's thumb and index finger, but not touching. Align the zero mark with the subjects fingers. The subject should indicate when they are ready. Without warning, release the ruler and let it drop - the subject must catch it as quickly as possible as soon as they see it fall. Record in meters the distance the ruler fell. Repeat several times (e.g. 10 times) and take the average score.
• Calculation: Calculate the average distance the meterstick fell. Use the table below to determine how long it took the ruler to fall the measured distance (distance in cm, time in seconds). The table is based on the following formula, where d = the distance the ruler fell in meters, g = the acceleration of gravity (9.8 m/s^2), and t = the time the ruler was falling (seconds)

t = sqrt ( 2d / g )

distance (cm) time (seconds) distance time distance time distance time
1 0.045 26 0.230 51 0.323 76 0.394
2 0.064 27 0.235 52 0.326 77 0.396
3 0.078 28 0.239 53 0.329 78 0.399
4 0.090 29 0.243 54 0.332 79 0.402
5 0.101 30 0.247 55 0.335 80 0.404
6 0.111 31 0.252 56 0.338 81 0.407
7 0.120 32 0.256 57 0.341 82 0.409
8 0.128 33 0.260 58 0.344 83 0.412
9 0.136 34 0.263 59 0.347 84 0.414
10 0.143 35 0.267 60 0.350 85 0.416
11 0.150 36 0.271 61 0.353 86 0.419
12 0.156 37 0.275 62 0.356 87 0.421
13 0.163 38 0.278 63 0.359 88 0.424
14 0.169 39 0.282 64 0.361 89 0.426
15 0.175 40 0.286 65 0.364 90 0.429
16 0.181 41 0.289 66 0.367 91 0.431
17 0.186 42 0.293 67 0.370 92 0.433
18 0.192 43 0.296 68 0.373 93 0.436
19 0.197 44 0.300 69 0.375 94 0.438
20 0.202 45 0.303 70 0.378 95 0.440
21 0.207 46 0.306 71 0.381 96 0.443
22 0.212 47 0.310 72 0.383 97 0.445
23 0.217 48 0.313 73 0.386 98 0.447
24 0.221 49 0.316 74 0.389 99 0.449
25 0.226 50 0.319 75 0.391 100 0.452
• scoring: There is a scoring table on the make your own Reaction Timer page where you can rate your score.
• target population: sports requiring good hand-eye coordination and quick reactions, such as race car driving, boxing and racket sports.
• variations: you could adapt this test to determine the reaction time to a sound, by using the set up with the subject wearing a blindfold, and the ruler being released at the same time as an auditory signal.
• comments: results for left and right hands can be expected to be different, therefore this should be controlled for or at least the hand used recorded with the results.

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