(light music) – Welcome to the Think Fast, Act Fast activity. In order to better understand how crashes occur, you’re going to explore human reaction time. So in this activity, you’re going to measure how well your muscular system and your nervous system work together to produce human reaction time. So let’s take a look at the supplies. You’re gonna have a ruler that has centimeter and millimeters in it. You’re gonna have a calculator with a square root function and your activity sheet that has the data table. Also, for a little fun, you can have a dollar bill handy, but you also need a volunteer. Can I have a volunteer? All right, so test your reaction time. We’re gonna see if you can catch this dollar bill, okay? So here’s how we’re gonna do it. Keep your fingers as far apart as the dollar is wide. All right, to start off with I’m gonna put President Washington right in the middle. Then when I drop it, you try to catch it, okay? – Okay. – Ooh, very close.
– I almost had it. – Almost had it. So now what we’re gonna do is substitute the ruler for the dollar bill. Same idea, your gonna put your fingers this time the width of the ruler. Instead of starting halfway down, I’m gonna start all the way the top. So that zero is right at the top of your fingers, okay? So now as I drop it, you’re gonna try to catch it as quickly as you can. Ready? Good. This is the measurement we want, right here. So see how much of the ruler fell through before she caught it? We’re right at 16 centimeters, and about five millimeters, okay. So write that — 16.5 centimeters. So make sure when you do your measurement that you are measuring to the nearest millimeter. Have fun.