Measurement technique & choosing instruments

Answer

The **smallest division** it can read (e.g. 1 mm on a metre rule, 0.01 mm on a micrometer). Finer resolution → smaller uncertainty.

Answer

A wrong reading caused by looking at the scale **from an angle** instead of straight on (at eye level).

Answer

The instrument **doesn't read zero** when it should, so every reading is off by that fixed amount.

Answer

Metre rule **1 mm**, vernier caliper **0.1 mm**, micrometer screw gauge **0.01 mm**.

Answer

Pick a resolution that is a **small fraction** of the quantity, so the fractional uncertainty stays small.

Answer

Measure a **stack of N sheets** and divide by N — the value **and** its absolute uncertainty both divide by N.

Answer

The fixed reaction-time uncertainty applies to the whole run, so dividing the total by 10 divides that absolute uncertainty by 10.

Answer

Add the **fractional** uncertainties: $\tfrac{\Delta y}{y} = \tfrac{\Delta a}{a} + \tfrac{\Delta b}{b} + \tfrac{\Delta c}{c}$ (given in the data booklet).

Answer

Multiply the fractional uncertainty by the power: $\tfrac{\Delta y}{y} = |n|\,\tfrac{\Delta a}{a}$ (given in the data booklet).

Answer

Add the **absolute** uncertainties: $\Delta y = \Delta a + \Delta b$ (derived, not in the booklet).

Answer

Read the **bottom of the meniscus** at **eye level** to avoid a parallax error.

Answer

A **justification by its resolution** — match the instrument's smallest division to the quantity, don't just name it.