foundations of physics

Question 1

What are SI units?

Answer 1

Fundamental (base) units of physical quantities.

Question 2

What is the SI unit of mass?

Answer 2

Kilogram - kg.

Question 3

What physical quantity is measured in mol?

Answer 3

Amount of substance.

Question 4

What is the SI unit of current?

Answer 4

Amperes (A).

Question 5

Is the SI unit for temperature ℃ or K ?

Answer 5

K (kelvin) as this is the absolute scale.

Question 6

What is the SI unit of length?

Answer 6

Metres - m.

Question 7

What quantity is measured in seconds?

Answer 7

Time.

Question 8

What multiplier is associated with the prefix kilo (k)?

Answer 8

1000 (10^3)

Question 9

What multiplier is associated with the prefix femto (f)?

Answer 9

10^-15

Question 10

What is accuracy?

Answer 10

● Accuracy is a measure of how close a
measured value is to the true, accepted value.
● If a experiment result is accurate it is very
close to the true value.
● In practice, the true value usually is not
known.

Question 11

What is validity?

Answer 11

A measurement is valid if it measures what it is
supposed to be measuring. An experimental
procedure is valid if the obtained values provide
an answer to the question that is being asked.

Question 12

What is a random error?

Answer 12

An error that occurs due to unexpected changes
during an experiment. These cannot be predicted
and they can cause repeated results to differ
from one another.

Question 13

What is an anomaly?

Answer 13

An anomaly (also known as an outlier) is a data
point or a value in a set of results that does not fit
the trend of the data and is therefore an
unexpected result. These can happen as a result
of random errors during an experiment.

Question 14

What is a systematic error?

Answer 14

An error that occurs due to faults in equipment or
experimental method. Systematic errors cause
the result to differ by the same amount each
time, making them predictable. They can occur
due to not calibrating an instrument correctly.

Question 15

State three ways of reducing random

errors.

Answer 15

● Take at least three repeats and calculate a
mean (this increases the likelihood of identifying
anomalies).
● Use computers/data loggers.
● Use higher resolution equipment.

Question 16

How can systematic error be reduced?

Answer 16

Calibrate apparatus before using e.g. zero the

balance when it is empty.

Question 17

Is electronic noise in the circuit of an ammeter

random error or systematic error?

Answer 17

Random error, as it will cause fluctuations in
readings that affect precision and it cannot be
removed.

Question 18

Why should you measure background radiation

before measuring the radioactivity of a source?

Answer 18

So that only the source’s radioactivity is
measured - by accounting for background
radiation, systematic error can be reduced.

Question 19

What is precision?

Answer 19

How consistent/close together repeat readings
are - the closer they are, the more precise they
are.

Question 20

What makes an experiment repeatable?

Answer 20

If the original experimenter can redo the
experiment with the same equipment and method
then get the same results, the experiment is
repeatable.

Question 21

What makes an experiment reproducible?

Answer 21

What makes an experiment reproducible?

Question 22

What is meant by resolution?

Answer 22

The smallest change in the quantity being
measured that gives a recognisable change in
reading

Question 23

What is absolute uncertainty?

Answer 23

Uncertainty given as a fixed quantity.

Question 24

How can percentage and fractional uncertainty be

reduced?

Answer 24

Measure larger quantities. For example, a longer
rope will have a smaller percentage uncertainty
than a shorter one.

Question 25

What is the difference between a reading

and a measurement?

Answer 25

Readings are when one value is found,
measurements are when the difference between
two readings is found.

Question 26

What is an order of magnitude?

Answer 26

Powers of ten which describe the size of an
object, and which can also be used to compare
the sizes of objects.

Question 27

What is the order of magnitude for the

diameter of a nucleus?

Answer 27

10^-15 (femtometres)

Question 28

What is meant by a scalar quantity?

Answer 28

A quantity that has only magnitude.

Question 29

What is a vector quantity?

Answer 29

A quantity that has magnitude as well as

direction.