# Using an Active Model to Measure Speed

By Laura Hospitál on Dec 04, 2015

This activity should be completed after introducing the definition and formula for speed (possibly the next day). In this activity, students will use a trundle wheel to measure distance and a stopwatch to measure time. My class walked around the hall, but any convenient location would work.

Related vocabulary:
• speed -  a measurement of how fast something moves, the rate of motion
• displacement - the change in position of an object
• Formula for speed - Speed = Distance / Time

## Preparation:

Only a trundle wheel, a stopwatch, and means to record data are necessary for this activity.

## Procedure

Warm Up:
1. Begin by discussing a common speed limit like 55 mph.  Ask the students what this means.
2. Discuss the unit miles PER hour.  This means that you will be traveling at 55 miles in one hour.
3. Explain to the class that they will be measuring speed in meters/second using the formula
Speed = Distance/Time   Please see Jim Clark's 3-variable formula triangle if students are having difficulty using the formula   http://www.perkinselearning.org/accessible-science/adapted-3-variable-formula-triangle   Distance measurement using the trundle wheel:  Measure several distances using the trundle wheel.  Have the each member of the class take a turn using the wheel.  Make sure to end up at the same spot if you also would like to discuss displacment (See variations.)    Time measurement using a stopwatch:  Have two members of the class measure time using a stopwatch.  The stopwatch feature on the iPAD or other idevice are particularly accessible for students with VI. This way the students can check each others' measurements.
1. Have one student (and the teacher) record the distance and the time when you arrive.
2. After returning to the room, calculate speed using the formula -  Speed = distance/ time
3. Convert from minutes to seconds if the stopwatch utilized does not indicate seconds.

## Variations

• For students who are also learning displacement, ask the class what the displacement was from the point where you began and the point where you ended.  If students don't understand that it was zero, discuss.
• Ask:  "If I was where we began our walk and you were where we ended, how much distance would be between us?"
• Students should answer that there would be no space, therefore displacement is zero.

## NGSS Standards:

Middle School - Forces and Inteactions
PS2.A: Forces and Motion
All positions of objects and the directions of forces and motions must be described in an arbitrarily chosen reference frame and arbitrarily chosen units of size. In order to share information with other people, these choices must also be shared. (MS-PS2-2) Read more about: