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Sports Physics 6-8 / Week 04 / Wednesday
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Week 04 · Gravity Pulls

Wednesday

Field Lab: The drop test
// The force that brings every ball back down
⏱ about 20 min

Wednesday: Field Lab: The Drop Test

Raven stands on the lawn, arms out at shoulder height. A tennis ball in one hand, a rolled sock in the other.

"Predict," she says. Rocket kneels below with the timer. "The ball lands first. It is heavier."

Nova hovers by Raven's hand. "Watch closely. And listen."

Raven lets go of both at once. Two soft thumps, almost one sound.

"Again," Rocket says, frowning. Three more drops. Each time the thumps land together.

"What do you notice?" Raven asks.

"My prediction was wrong," Rocket says. "Heavy and light fell together. Just like the hammer and the feather."

Your mission

Today you run two tests. First, you drop a tennis ball and a rolled sock together and see which lands first.

Second, you time the tennis ball falling from two heights: knee height and shoulder height.

Predict both results before you start. Then let the drops decide.

  • A tennis ball and a rolled pair of socks
  • A kitchen timer or phone stopwatch, and a partner to run it
  • Masking tape to mark knee height and shoulder height on a wall or fence
  • A hard, flat landing spot: a driveway, patio or cleared hallway floor
  • Your Field Log and a pencil
Safety first
Drop only from the height you can reach standing on the floor. Never climb a chair, step, ladder or railing.
Use only a tennis ball, a foam ball or a rolled sock. Nothing is thrown at anyone.
Keep toes, pets and younger children away from the landing spot.
Work outdoors or in a cleared hallway, away from windows and roads. A grown-up picks the spot.
  1. Mark knee height and shoulder height on a wall or fence with small pieces of tape.
  2. Predict: dropped together from shoulder height, which lands first, the ball or the sock?
  3. Hold the ball and the sock side by side at shoulder height. Let go of both at the same instant.
  4. Watch and listen. Record which landed first, or whether they landed together. Repeat four more times.
  5. Now time the ball alone. Hold it at knee height. Your partner starts the timer at "go" and stops it at the thump.
  6. Record the time. Repeat twice more and average the three.
  7. Hold the ball at shoulder height and repeat the three timed drops. Record and average.
  8. Compare the two averages. Which fall took longer?
PREDICT BEFORE YOU DROP
  • Read the question.
  • Tap your answer.
A tennis ball and a rolled sock are dropped together from the same height. A physics text predicts they will:
Which fall should take longer: from knee height or from shoulder height?
Your timed falls are all under one second and wobble a lot. Why?
TestMy predictionTrial 1Trial 2Trial 3Result or average
Ball and sock together, shoulder height
Ball alone from knee height (seconds)
Ball alone from shoulder height (seconds)

Reading the result

The ball and the sock most likely landed together, or so close you could not tell. That matches the physics text.

Both are small and fall a short way, so air resistance barely matters. Gravity speeds them up the same.

The shoulder height fall should have taken a little longer than the knee height fall. It had farther to go.

Your times will be short, well under one second, and will wobble. Hand timing cannot catch tenths of a second well.

That is why you averaged. Scientists repeat trials for exactly this reason, and they report how much the numbers varied.

What the lab showsTrue or false?
The heavier tennis ball landed long before the rolled sock.?
A fall from shoulder height takes longer than a fall from knee height.?
Hand timing of a short fall is exact to the hundredth of a second.?
Gravity sped up the ball and the sock by the same amount.?
WHY THIS EXERCISEThe drop test is your own evidence that gravity pulls on every mass the same way.
How many times did you drop the ball and the sock together? Type a number.
WHY THIS EXERCISEFive drops turn one surprising result into a pattern you can trust.
Draw Raven's two hands letting go of the ball and the sock, and the two thumps landing together.

Careful dropping. Tomorrow you will read NASA's table of how hard each planet pulls.

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