demonstrations:acceleration_due_to_gravity_with_a_ticker_timer
Acceleration Due to Gravity with a Ticker Timer
Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★★☆ Can be done by science teachers
Safety: ★☆☆ Minimal safety procedures required
Categories: Force, Motion
Alternative titles: Measuring g Using Ticker Tape
Summary
Use a ticker timer and tape attached to a mass to record the motion of a falling object. By measuring equal time intervals on the tape, you calculate speeds and accelerations and estimate g.
Procedure
- Set a ticker timer to 50 Hz (0.02 s per dot).
- Thread a 1 m length of ticker tape through the timer so ~10–15 cm extends past the carbon disk.
- Firmly tape the free end of the ticker tape to a 200g mass; ensure the tape exits the timer smoothly with minimal friction.
- Position the timer on its side at the bench edge so the tape falls freely to the floor without rubbing.
- Switch on the timer, hold the mass ~1 m above the floor, then release it so the tape runs through while it falls; stop the timer after the mass lands.
- Measure 5 dot sections and use the results to calculation acceleration due to gravity.
Links
Ticker Timer Free Fall Video - Juddy Productions:
📄 Acceleration Due To Gravity - Liacos Educational Media: https://www.liacoseducationalmedia.com/Acceleration_Due_To_Gravity_(Ticker_Timers)-Liacos_Educational_Media.pdf
Variations
- Use different masses to see that g is mass-independent (air resistance permitting).
- Increase drop height to obtain more intervals and a better line of best fit.
- Replace with a motion sensor or video tracker and compare g values.
Safety Precautions
- Keep feet clear of the falling mass; use a soft landing pad or catch safely near the floor.
- Secure the timer so it cannot fall from the bench.
- Keep fingers away from the moving tape and carbon/disc.
- If using a mains ticker timer, ensure RCD protection and teacher supervision; switch off before threading tape.
- Clear the drop zone of obstacles.
Questions to Consider
- What should the speed–time graph look like for free fall without air resistance? (A straight line through or near the origin with positive slope; slope ≈ g.)
- Why might the best-fit line not pass exactly through the origin? (Start-up friction, first few unclear dots, slack in tape, reaction timing, calibration error.)
- What do the Speed (interval) values and Acceleration values indicate about falling objects? (Speeds increase by roughly equal amounts each equal time step; acceleration is approximately constant and ≈ g.)
- If air resistance becomes significant, how would the speed–time graph change? (It would curve, slope decreases over time, approaching terminal speed.)