# How Fast is that? Ice Skaters 1

#### Summary

## Learning Goals

Students will:

- Follow the motion of an object whose distance traveled is longer then its displacement
- Determine the displacement of a person or object who crosses both lines
- Convert number of frames into a time interval to determine the elapsed time for a person to cross both lines
- Calculate the average velocity for the person
- Observe when an object travels faster or slower than its average velocity
- Find something that has a negative velocity

## Context for Use

This activity is intended to introduce students to the concepts of displacement, average velocity, and direction. It requires no background knowledge in these concepts, but does assume that students know how to open a Direct Measurement Video (DMV) and step through it frame-by-frame. It also presupposes a knowledge of basic unit conversion.

If students have some experience analyzing Direct Measurement Videos, this activity should take about 20 minutes.

## Description and Teaching Materials

Here is a worksheet (Microsoft Word 2007 (.docx) 2MB Aug22 14) to guide students through this activity:

worksheet solutions (Microsoft Word 2007 (.docx) 2MB Aug22 14)

These instructions are highly scaffolded, giving students step-by-step instructions. An instructor may chose to provide less detailed instructions to encourage independent thinking and problem solving.

## Teaching Notes and Tips

Sometimes student will start counting frames immediately even though the first questions are about displacement.

Although I like for my students to know how to convert from m/s to mph, after they have mastered that skill I encourage them to find a faster way (Google for example) to do the conversion so they can check their answer. It's also nice for them to know that the speed in mph is just over double the corresponding value in mph.