Maths skills, measurement and uncertainty

What are the base quantities?

Length (m)

Mass (kg)

Temperature (K)

Time (s)

Current (A)

Quantity of substance (mol)

What are the unit prefixes? (order from largest to smallest)

Tera ×10^12

Giga ×10^9

Mega ×10^6

Kilo ×10³

Centi ×10²

Milli ×10^-3

Micro ×10^-6

Nano ×10^-9

Pico ×10^-12

Fento ×10^-15

What is engineering notation?

Always has the power as a multiple of three (to match the rpefixes)

What is the definition of precision?

Measure of how close a set of repeated measurements are to eachother.

What is the definition of accuracy?

Measure of how close a measurement is to the true value.

What is the resolution?

The smallest unit in a measured quantity a device can display.

What is the minimum uncertainty?

Half the resolution.

What is a reading?

A single value from an instrument with a fixed 0.

What is a measurement?

Difference between two values (has two readings , a start and end).

What is the definition of repeatability?

The person that made the experiment is able to repeat it and achieve similar results.

What is the definition of reproducability?

A different person is able to repeat an experiment and achieve similar results.

What is random error?

Random usually to do with the user (e.g bad eyesight, parallax error)

Can be fixed by calculating a mean from repeated readings.

Affects the precision.

What is systematic error?

Results are wrong by the same amount every time/ consistent (e.g zero error )

Can be fixed by calibrating equipment/ checking for zero error.

Affects accuracy.

What are parallax errors?

The equipment shoes the correct result but the user is not perceiving it correctly.

(e.g not looking at a scale perpendicular, instead looking at it from an angle)

What is absolute uncertainty?

the actual amount by which the quantity is uncertain

(e.g ±0.1)

What is percentage uncertainty?

(uncertainty/ measured value ) x 100

How do you combine uncertainty when adding/subtracting data?

Add the absolute uncertainties.

How do you combine uncertainty when multiplying/dividing data?

Add the percentage uncertainties.