A Level Physics chapter 2: practical skills

What is the formula for the *percentage uncertainty*?

percentage uncertainty = uncertainty (or spread) ÷ measured value
all x100%

Define *"systematic error"*

This is an error that is always the same for each repeat - usually because of an error in the equipment used

Define *"random error"*

often caused by human error eg measurement in timing or misjudgement.

Define *"zero error"*

when a piece of measuring equipment should be reading zero. But doesn't

Define *"anomaly"*

a result that does not fit the pattern

Define *"continuous variable"*

a variable which can have any numerical value.
e.g. temperature, length

Define *"resolution*

the smallest change that can be read from a measuring device.

Explain the difference between *prediction* and *hypothesis*

Prediction is more specific than a Hypothesis

When is a measurement described as *"accuarate"*?

A measurement is described as "accurate" if the value obtained is close to the true value

Define *"independent variable"*

the variable that can be changed by the experimenter, there should only every be *one independent variable*

e.g. mass

Where is the independent variable plotted when drawing a graph?

on the *x-axis*

Define *dependent variable*

this variable is measured by the experimenter. This variable is *completely dependent on the independent variable*. There is no choice in this variable.

e.g. time

Where is the dependent variable plotted when drawing a graph?

on the *y-axis*

Define *"controlled variable"*

these variables must be kept the same throughout the entire experiment.

e.g. temperature of room, length of spring, friction etc...

Define *"precision"*

the precision of a measurement is the degree of exactness (sometimes the number of significant figures) to which the measurement of a quantity or value can be obtained and reproduced consistently.

Define *"precision of an instrument"*

the precision of an instrument is the smallest non-zero reading that can be measured using the instrument

Define *"accuracy"*

Accuracy is a measure of confidence in an accurate measurement, often expressed as and upper and lower limit of the measurement based on the *uncertainty* in the measurement.

e.g. g = 9.8±0.3ms-²

Define *"accurate measurements"*

a measurement which can be described as accurate is one that has been obtained using accurately calibrated instruments correctly and where no systematic errors arise

scalar quantities

examples include mass, temperature and speed

vector quantities

examples include weight, acceleration and displacement