Physics 11–12 · Year 12

Projectile motion: primary data from a ball leaving a bench and a spring launcher (syllabus practical)

Module 5: Advanced Mechanics (Projectile Motion)

Practical, model not builtLow risk

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The idea

A projectile's horizontal velocity stays constant while its vertical velocity changes at g, so range and time of flight follow from the launch conditions.

What you need

Steel ball (16 mm), a curved ramp clamped at the bench edge so the ball is launched horizontally, carbon paper and plain paper on the floor, plumb line, metre rule, light gate at the bench edge
Alternative: spring-loaded projectile launcher with angle scale, or a ball thrown against a uniform backdrop filmed on a phone for Tracker analysis (the NSW Department of Education Module 5 guide)

How to do it

Measure the bench height h with the plumb line marking the launch point on the floor.
Release the ball from a marked height on the ramp; read its launch speed from the light gate and its landing point from the carbon mark; five trials per release height.
Predict the range from R = u sqrt(2h/g) before measuring, then compare.
Repeat for three release heights (three launch speeds) and plot range against launch speed.
Launcher version: fire from floor level at 30, 45 and 60 degrees at fixed speed, measure range and time of flight from video, and compare with the derived relationships.

What you should see

From a 0.900 m bench a ball leaving at 1.50 m/s is in the air for 0.428 s, lands 0.643 m out and hits the floor with a vertical speed of 4.20 m/s (g = 9.806 65 m/s^2). Range is proportional to launch speed, and the plot is a straight line through the origin; at fixed speed, landing at the launch height, 45 degrees gives the longest range and 30 and 60 degrees give equal ranges. Because the launch speed is measured at the bench edge, ramp friction does not affect the prediction; the learner knows it worked when predicted and measured ranges agree within about 5 per cent, the main uncertainties being the light-gate timing and the landing mark.

What changes

What you change: launch speed (or launch angle)
What you measure: horizontal range and time of flight
What you keep the same: launch height
same ball
launch direction horizontal or angle fixed

Common misconceptions

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

A projectile needs a forward force to keep moving; after launch only gravity acts.
At the top of the flight the projectile has zero velocity; only its vertical component is zero.

Safety card

Low riskLearners carry it out

Hazards

steel ball on the floor as a trip hazard
launcher spring

Controls

clear landing zone, collect the ball after each trial
never look down a loaded launcher

Note

Record the activity in RiskAssess (https://www.riskassess.com.au/) and follow the Science ASSIST risk management information sheet (https://asta.edu.au/resource/ais-risk-management-and-risk-assessment/).

Curriculum references

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

Physics Stage 6 Syllabus (2017), current: Year 11 until the end of 2026, Year 12 until Term 3 2027PH12-12 PH11/12-4 PH11/12-5 PH11/12-6
Physics 11-12 Syllabus (2025), not yet taught: Year 11 from Term 1 2027, Year 12 from Term 4 2027, first HSC examination 2028PY-12-01 PY-12WS-05
Australian Curriculum v9No Australian Curriculum v9 code is listed.

Sources

The pages the author read to write this activity.

All Concept Studio activities