Speed and Acceleration (Copy)

1. Core Concepts

• Speed is how fast something is moving.
  → Speed = distance / time
  → Unit: m/s or cm/s
• Velocity is speed with direction (used for acceleration)
• Acceleration is the rate of change of velocity.
  → a = (v - u) / t
  → Units: m/s²

 2. Objective of the Experiment

• To measure the speed of a moving object (e.g. trolley or ball)
• To determine the object’s acceleration
• To investigate how a factor (e.g. mass, force, incline) affects motion

 3. Apparatus Required

 4. Method – Measuring Speed

 Using a Stopwatch

1. Measure a known distance (e.g. 1.00 m) with metre rule
2. Let trolley move across distance
3. Start stopwatch as trolley passes start line, stop at end
4. Calculate:
   Speed = distance / time

✔️ Repeat multiple times and take average time
✔️ Start stopwatch only after object begins moving

 Using Light Gates (More accurate)

1. Place two light gates 1.00 m apart
2. Attach card (e.g. 10 cm) on trolley
3. Light gates record time when card passes through each
4. Use:
   Speed = distance / time

✔️ Light gates reduce reaction time error
✔️ Used especially for short time intervals or fast motion

 5. Method – Measuring Acceleration

Use the formula:
a = (v - u) / t

 Using Ticker Timer or Light Gates

With ticker tape:

• Ticker tape marks at regular intervals (e.g. 50 Hz → 0.02 s between dots)
• Measure increasing distances between dots to show acceleration
• Plot velocity vs time graph → gradient = acceleration

With light gates:

• Set up 3 gates:
  • Gate 1 and 2 measure initial speed u
  • Gate 2 and 3 measure final speed v
• Time between them = t
• Use formula to calculate a

 6. Equations to Remember

1. Speed = distance / time
2. Acceleration = (final velocity - initial velocity) / time
3. For constant acceleration:
   v² = u² + 2as
s = ut + 0.5at²

 7. Graphical Questions

 8. Example Data Table

✔️ Plot speed vs time to calculate acceleration from gradient
✔️ Use best-fit line where trend is expected

 9. Variables

 10. Common Errors to Avoid

 11. Improvement Suggestions

• Use light gates instead of stopwatch
• Repeat and take average time
• Use longer distances for more measurable times
• Use data logger or ticker timer for better timing precision

 12. ATP-Style Question Types

13. Final ATP Exam Tips

• Quote readings with units and correct decimal places
• If object starts from rest, write u = 0
• Label graph axes with quantity and unit
• For gradient:
  → Choose two points far apart
  → Use Δy / Δx with units
• Always state:
  

  “Repeat the experiment and average the times to improve reliability.”