Academic journal article The Science Teacher

Getting Up to Speed

Academic journal article The Science Teacher

Getting Up to Speed

Article excerpt

A common high school physics or physical science activity asks students to calculate their walking speeds using the following equation:

speed = distance / time.

I adapted this activity and three accompanying extensions for use in a single, 50-minute class period. Students work in pairs on an athletic field or in the school's hallways and--using stopwatches and metersticks--measure distances, mark the distances with tape, and measure the time it takes each other to walk those distances.

Activity how-to

I don't give step-by-step instructions, but I watch students to see what they do. If I observe blatant errors, I intervene by asking questions to try to guide students toward better methods. For example, a common problem is they tend to use too short distances, which affects their timing: I have had students try to measure the time it takes them to walk 1 meter! Teenagers can also be very social and often want to walk with friends, causing them to adjust their walking speeds to match their partners'. To combat this, I instruct students to walk alone.

Although students calculate their walking speeds in meters per second, I have them convert to miles per hour, using the conversion

1 m/s = 2.24 mph.

Some teachers may prefer to keep speeds in metric units, but I have found that students enjoy comparing their walking speeds to that of driving a car. A typical walking speed is 1.3 m/s or 3.0 mph.

When students return to the classroom, they record their walking speeds on the class chart or spreadsheet. Males and females record their speeds in different colors to see whether there are any gender-based differences. Usually, the males have slightly faster walking speeds because, on average, they are taller and have longer stride lengths.

Follow-up questions for this activity include "Is the speed you measured an average or instantaneous speed?" and "What additional information would you need to determine your walking velocity?" Students could also plot their walking speeds as a function of height to see whether a relationship exists between the two. This could be completed in an additional class period or assigned as homework.

I also use three activity extensions, which I describe below. I caution students not to change their walking speeds for these extensions. …

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