Science and Technology K–6 · Year 4

Drop race: a heavy ball and a light ball land together

Science understanding: Physical sciences

Practical, model not builtLow risk

This site has no interactive model of its own. Where a step or a material names a Concept Studio model, simulation or tool, it has not been built; an external simulation a step names (for example PhET) is not part of this site.

The idea

Gravity pulls every object toward the Earth with the same acceleration, so two balls of different mass dropped together land together unless air resistance is large.

What you need

a golf ball and a table-tennis ball (same size, very different mass)
a tennis ball and a cricket ball
2 sheets of A4 paper, one flat and one crumpled tight
a 2.00 m drop height marked on a wall
a phone camera with slow-motion video (optional)

How to do it

Predict which of the golf ball and table-tennis ball will land first, and write the reason.
Hold both at the 2 m mark, release them at the same instant and listen for the landing sounds. Repeat five times.
Repeat with the tennis ball and cricket ball.
Drop the flat sheet and the crumpled sheet together. Repeat five times.
If a camera is available, film a drop in slow motion and count frames to the landing.
Explain the paper result using air resistance and the ball results using gravity.

What you should see

From 2.00 m with g = 9.8 m/s^2 the fall takes 0.639 s for any mass. With air resistance added, the model puts the 2.7 g table-tennis ball about 0.03 s behind the golf ball (0.667 s against 0.641 s), a gap too small to see and hard to hear, and the tennis and cricket balls land within 0.003 s of each other; unevenness in the release is usually larger than these gaps. The flat sheet takes about 2 s or longer (the model gives 2.0 s for a 5 g A4 sheet falling flat, and a real sheet flutters and slides sideways), while the crumpled sheet lands close behind the balls (about 0.66 s in the model for a paper ball 4 to 6 cm across): same mass, different air resistance, because the flat sheet presents a large area.

What changes

What you change: mass of the object (balls) or shape (paper)
What you measure: which lands first and the fall time
What you keep the same: drop height
release at the same instant
no throw

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

Heavier things fall faster.
The crumpled paper falls faster because crumpling made it heavier.
Gravity is stronger on heavier objects so they speed up more (the force is larger, and so is the mass to be moved; the acceleration is the same).

Safety card

Low riskLearners carry it out

Hazards

cricket ball on feet

Controls

drop onto a mat
stand clear of the landing zone

Note

Risk assessment before the lesson using Primary RiskAssess or the school's own template.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Science and Technology K-6 Syllabus (2017), current, taught until 2026; code read from the syllabus document on 22 September 2026ST2-9PW-ST ST2-1WS-S
Science and Technology K-6 Syllabus (2024), implemented from 2027; NESA's timeline is 2026 plan and prepare and 2027 start teaching, and schools may choose to implement it during 2026; Stage 2 content: demonstrate the force of attraction between objects and Earth (gravity), under 'The Sun is the centre of our solar system and provides our world with energy'; code read from the outcomes page and the content read from the Stage 2 content page on 22 September 2026ST2-SCI-01
Australian Curriculum v9AC9S4U03AC9S4H01AC9S4I01AC9S4I05

Sources

The pages the author read to write this activity.

All Concept Studio activities