Reaction time adds uncertainty mainly to:

  1. the reading of a thermometer
  2. measurements of time with a hand-held stopwatch
  3. the mass of a block
  4. the length of a rod
Answer

B) measurements of time with a hand-held stopwatch

Human reaction time is about 0.1–0.3 s. SLO P-11-A-07 · Understanding

Physics MCQ · More Physical Quantities and Measurement MCQs · Practise