# Measuring Velocity: An active model

By Laura Hospitál on Jan 24, 2016

Students will measure distance traveled and time traveled to determine velocity in a similar manner to speed determination in the recent activity:  Using an Active Model to Measure Speed found at http://www.perkinselearning.org/accessible-science/using-active-model-measure-speed  However, velocity differs from speed in that it is a vector quantity and includes a direction.

This activity should follow the above-mentioned activity, ideally within a day or two so that content from the speed activity is still fresh in the students' minds. It should also immediately follow instruction on velocity.

### Related Vocabulary

• Speed: a measurement of how fast something moves, the rate of motion
• Formula for speed:  Speed = Distance / Time
• Velocity:  the speed of an object in a particular direction
• Vector:  a quantity that has both size and direction

## Preparation:

• The instructor will simply need to gather materials for this activity and willing participants.
• A trundle wheel, a stopwatch, and the means to record data are all that are necessary for this activity.

## Procedure

### Warm-Up:

Have students prepare to complete a written warm-up.  Ask students what information was necessary to determine speed.  Have students write down what was measured and the formula used.  In this manner all students have the opportunity to respond. Discuss only after all students are done.  Tell students that today we will measure not only speed, but also velocity.  Ask students to remember the prior lesson:  What else will be part of this measurement?  Discuss:  Velocity is determined by dividing distance by time (like speed), but includes direction as well.

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

### Determining Velocity:

• Before beginning this activity, talk about which directions you will be walking.  Choose at least two different directions and measure distance and time in each direction.  Discuss cardinal directions if necessary.
• Distance and time will be measured in a manner similar to the measurement of speed, however direction will be included in the measurement of velocity.

#### Distance measurement using the trundle wheel:

• Measure distance traveled in a known direction.  If necessary, a compass may be utilized.  One student should be responsible for taking this measurement and counting clicks on the trundle wheel.

#### 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 visual impairments. This allows students to check each others' measurements.

#### Calculation of speed

• After returning to the room, calculate speed in m/sec using the formual Speed = distance/time.  Convert from minutes to seconds as necessary.
• Have students work in groups to determine speed for each trial or have them work independently if time and math skills allow.

### Closure: Calculation of Velocity

• Ask students:  "What do we need to do with these measurements now to deterine velocity?"
• Discuss. Students will take each of the measurements and convert from speed to velocity by adding the direction.  Example:  .75 m/sec= speed  .75 m/sec east = velocity
• Review the terms speed, velocity, and vector from the vocabulary section above.

## 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)