# Measuring Speed

By Laura Hospitál on Jan 16, 2017

Students measure the distance a marble rolls and the time it takes to roll. They then calculate the speed using the equation: Speed = Distance / Time.

## Preparation:

Gather the materials for the lab.

## Procedure

Please see the pictures on this page and the video below for clarification of set up of lab.

1. Find a space on the counter or table with over a meter space available
2. Place 2 books on one end of the desk.
3. Lean the grooved ruler (groove up) on the books.
4. Place another book at the end of the desk.  This book will stop the marble.
5. Measure the distance from the end of the grooved ruler on the desk to the book at the other end of the desk.  The is the distance that the marble will roll.  Record this distance.
6. Prepare the Stopwatch
7. Prepare to begin timing and roll the marble down the grooved ruler.
8. Start calculating time with the stopwatch when the marble hits the table.  See Accessible Time Tracking.  (See recent adaptation for using sound instead of vision for this task.)
9. Record the time traveled.
10. Using the formula Speed = Distance / Time, calculate speed in m/ sec. It will be necessary to convert from cm to m.
11. Repeat  #6-#10 two more times.
12. Calculate the average of the three speed calculations.

## Variations

• If there are two groups of students, have one group use more books in step 2 ( to lean the ruler/ramp on) and have the other group use less.
• Device a hypothesis as to which marble will roll faster and compare average speeds.
• If converting from cm to m poses a significant challenge to the students, speed can be calculated in cm/ sec.
• When measuring speed given an auditory cue, it is often more accurate  to use the auditory input rather than the visual input to start and stop the stopwatch.  For instance in this lab, my teaching assistant, Craig Edgley, measured within .15 seconds each trial using auditory input compared with measurements that varied much more significantly when sighted assistance was utilized. This may be something to keep in mind when considering new ways in which a student with visual impairment can participate in labs with his/her sighted peers.

## NGSS Standards:

Middle School - Forces and Interactions

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)