# Measuring Reaction Time with a Simple Device

• lgen0290
In summary, the conversation discusses a simple device for measuring reaction time which involves a cardboard strip with marked dots. The person conducting the experiment should position their thumb and forefinger at the left dot and try to pinch the strip as soon as possible after it begins to fall. The mark where the strip is pinched gives the reaction time. The conversation then goes on to discuss the equation used to calculate the distance from the lower dot to the 50.0 ms mark, with some discrepancies arising from incorrect conversions. The final conclusion is that the reaction time after 50 ms is 1.225 cm, not 122.5 cm as initially thought.
lgen0290

## Homework Statement

The figure below shows a simple device for measuring your reaction time. It consists of a cardboard strip marked with a scale and two large dots. A friend holds the strip vertically, with thumb and forefinger at the dot on the right in the figure below. You then position your thumb and forefinger at the other dot (on the left in the figure), being careful not to touch the strip. Your friend releases the strip, and you try to pinch it as soon as possible after you see it begin to fall. The mark at the place where you pinch the strip gives your reaction time.
(a) How far from the lower dot should you place the 50.0 ms mark?

## The Attempt at a Solution

I tried to use the equation h=1/2gt.
I got 24.5 cm=(.5)9.8m/s(5s)

Looking at it further, it seems that is 24.5 m, not cm, so I'm not sure. 24.5 meters is not right for sure, and neither is 24.5 cm.

lgen0290 said:
[b
I tried to use the equation h=1/2gt.

It should be (1/2)gt^2.

But wouldn't that make the number even bigger? Is the reaction time after 50 ms really 122.5 cm? It just doesn't sound right.

lgen0290 said:
But wouldn't that make the number even bigger? Is the reaction time after 50 ms really 122.5 cm? It just doesn't sound right.

You are right -- it doesn't. But the value comes out to be 1.225 cm, which does. Please at least do your arithmetic correctly.

Thanks. You could have simply pointed out that my conversion was incorrect on the seconds.

Sorry. I didn't mean to be rude, but so many people take our help for granted . I'm sure you are not one of them, and your mistake was genuine. We are , I hope.

## 1. What is reaction time and why is it important to measure?

Reaction time is the amount of time it takes for a person to respond to a stimulus. It is important to measure because it can provide information about a person's cognitive abilities, such as attention, processing speed, and decision making.

## 2. How can a simple device be used to measure reaction time?

A simple device, such as a ruler or a stopwatch, can be used to measure reaction time by having the person react to a stimulus, such as a sound or a visual cue, and recording the time it takes for them to respond.

## 3. What factors can affect reaction time measurements?

Reaction time can be affected by various factors, including age, gender, fatigue, distractions, and even the type of stimulus used. It is important to control for these factors when measuring reaction time.

## 4. How can measuring reaction time be helpful in different fields of study?

Measuring reaction time can be helpful in a variety of fields, such as psychology, sports science, and human factors engineering. It can provide insights into a person's cognitive abilities, physical performance, and reaction to different stimuli.

## 5. Are there any limitations to using a simple device to measure reaction time?

While a simple device can provide a quick and easy way to measure reaction time, it may not be as precise or accurate as more advanced equipment. Additionally, it may not be suitable for measuring reaction time in certain populations, such as individuals with motor impairments.

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