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Sports Physics 6-8 / Week 01 / Game Day
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Week 01 · Measuring Motion

Game Day

Game Day: Family speed trials
// Speed is distance divided by time
⏱ about 20 min

Game Day: Family Speed Trials

Saturday morning, the whole family gathers at the Field. Rocket has the timer. Raven has the Field Log open.

"Everyone walks, everyone jogs, and the ball goes last," Rocket announces. "Same ten metres for all."

A younger cousin wants to hop instead. "Hopping counts," Raven says. "It is a motion. We measure it."

Nova hovers above the start tape, flashing once when each racer leaves the line.

The numbers pile up in the log. "What do you notice?" Raven asks. "The walks are all close together."

"Everyone walks about the same speed," Rocket says. "But the jogs are all over the place."

Nova hums. "Now you have data from a whole family."

  1. Speed is the rate at which an object changes its location: distance divided by time.
  2. The SI units are the metre for length, the second for time and the kilogram for mass.
  3. Shared units let other people check your numbers. A step is not a shared unit.
  4. A brisk walk is about 2.9 metres per second, according to an OpenStax example.
  5. Every motion is described against a reference frame, and you must say which one you used.
◇ FAMILY SPEED TRIALS
Set up the Field: two tape lines 10 metres apart, or 5 metres in a hallway.
Each family member walks, then jogs, between the lines while someone runs the timer.
Record every time in the Field Log. Divide the distance by each time to find the speed.
Roll a soft ball along the same stretch and time it. Compare it with the walks and jogs.
Talk it over: which motions were close together, and which were spread out?
For a grown-up
Pick a flat, clear spot away from roads, stairs and windows. Jogging is only for those who feel steady on their feet.
Only soft balls are rolled, never thrown. Everyone wears shoes outdoors.
The speed facts this week come from an OpenStax physics text and the unit facts from NIST, at nist.gov.
Safety first
Clear the Field of anything that could trip a runner. Stop if anyone is tired or hurt.
Nothing is thrown. The ball is rolled along the ground.
Drink water on a hot day and rest between trials.
THINK IT THROUGH
  • Read the question.
  • Tap your answer.
Two family members jog the same 10 metres. One takes 3 seconds and one takes 4. Who was faster?
A cousin hops the Field in 5 seconds. Over 10 metres, what is the speed?
Game Day checkTrue or false?
Speed is distance divided by time.?
Hopping is a motion that can be measured.?
Metres per second is the SI unit of speed.?
A speed is meaningful without saying what it was measured against.?
WHY THIS EXERCISEEvery speed needs a distance, a time, a unit and a reference frame.
Draw a bar chart of every family member's walking speed. Label each bar in metres per second.
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