Physics 1 - Measurements and Their Errors

Question 1

What are SI units?

Answer 1

Fundamental (base) units of physical quatities.

Question 2

What is the SI unit of mass?

Answer 2

Kilograms (kg)

Question 3

What physical quantity is measured in mol?

Answer 3

The amount of a substance.

Question 4

What is the SI unit of current?

Answer 4

Amperes (A)

Question 5

Which is SI unit for temperature; °C or K?

Answer 5

Kelvin (K)

This is because kelvin is the absolute scale.

Question 6

What is the SI unit of length?

Answer 6

Metres (m)

Question 7

What is the SI unit of time?

Answer 7

Seconds (s)

Question 8

Are Newtons (N) an SI unit?

Answer 8

No newtons are not fundamental.

Question 9

What is the SI unit of force?

Answer 9

kilogram meters per second per second, or per second-squared (kgms⁻²)

Question 10

What is the SI unit of energy?

Answer 10

kilogram meters-squared per second-squared (kgm²s⁻²)

Question 11

Derive the SI units of energy.

Answer 11

(Kinetic energy) = ½×(mass)×(velocity)
Units=kg×(ms⁻¹)²
=kgm²s⁻²

Question 12

Derive the SI units of force.

Answer 12

(Force)=(Mass)×(Acceleration)
Units=kg×ms⁻²
=kgms⁻²

Question 13

What is the prefix -kilo in standard form and what letter/symbol is used to represent it?

Answer 13

×10³

k

Question 14

What is the prefix -mega in standard form and what letter/symbol is used to represent it?

Answer 14

×10⁶

M

Question 15

What is the prefix -giga in standard form and what letter/symbol is used to represent it?

Answer 15

×10⁹

G

Question 16

What is the prefix -tera in standard form and what letter/symbol is used to represent it?

Answer 16

×10¹²

T

Question 17

What is the prefix -peta in standard form and what letter/symbol is used to represent it?

Answer 17

×10¹⁵

P

Question 18

What is the prefix -milli in standard form and what letter/symbol is used to represent it?

Answer 18

×10⁻³

m

Question 19

What is the prefix -micro in standard form and what letter/symbol is used to represent it?

Answer 19

×10⁻⁶

μ

Question 20

What is the prefix -nano in standard form and what letter/symbol is used to represent it?

Answer 20

×10⁻⁹

n

Question 21

What is the prefix -pico in standard form and what letter/symbol is used to represent it?

Answer 21

×10⁻¹²

p

Question 22

What is the prefix -femto in standard form and what letter/symbol is used to represent it?

Answer 22

×10⁻¹⁵

f

Question 23

What is a random error?

Answer 23

An error that effects precision and cannot be completely removed, it causes differences in measurements.

Question 24

What is a systematic error?

Answer 24

An error that effects accuracy and occurs because of faults in equipment or experimental method, causing the result to be too large/small by the same amount each time.

Question 25

What are 3 ways to reduce random error?

Answer 25

Take at least 3 repeats and calculate a mean. Use a computer or a data logger. Use higher resolution equipment.

Question 26

State a cause of parallax error.

Answer 26

Reading a scale at a different angle each time, to correct this you should read scales at eye level to reduce parallax error.

Question 27

How can systematic error be reduced?

Answer 27

Calibrate apparatus before using it, such as zeroing the balance when it is empty.

Question 28

Is electronic noise in the circuit of an ammeter random error or systematic error?

Answer 28

It is a random error as it will cause fluctuations in readings that affect precision and it cannot be removed.

Question 29

Why should background radiation be measured before measuring the radioactivity of a source?

Answer 29

So that the actual radioactivity of the source is measured, rather than both the source and background radiation, by accounting for the amount of background radiation, thus reducing systematic error.

Question 30

What is precision?

Answer 30

Precise measurements are consistent, they fluctuate slightly about a mean value- precise doesn't indicate the value is accurate.

Question 31

What is repeatability?

Answer 31

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

Question 32

What is reproducibility?

Answer 32

If the experiment is redone by a different person with different techniques and equipment and the same results are found, it is repeatable.

Question 33

What is meant by resolution?

Answer 33

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

Question 34

What is meant if a value is accurate?

Answer 34

The value is close to the true value.

Question 35

What is absolute uncertainty?

Answer 35

Uncertainty given as a fixed quantity, which, when combined with a reported value, gives a range of values which should contain the true value.

Question 36

What is percentage uncertainty?

Answer 36

The absolute uncertainty, compared to the reported value, given as a percentage.

Question 37

What is the formula for percentage uncertainty and what are its units?

Answer 37

(%uncertainty)=((absolute uncertainty)÷(reported value))×100 | It has no units, since absolute uncertainty has the same units as the reported value.

Question 38

What is fractional uncertainty?

Answer 38

The absolute uncertainty, compared to the reported value, given as a fraction.

Question 39

What is the formula for fractional uncertainty and what are its units?

Answer 39

(fractional uncertainty)=(absolute uncertainty)÷(reported value) It has no units, since absolute uncertainty has the same units as the reported value.

Question 40

How can percentage and fractional uncertainty be reduced?

Answer 40

Measure larger quantities, for example, a longer rope will have a smaller percentage uncertainty than a shorter rope

Question 41

What is the difference between a reading and a measurement?

Answer 41

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

Question 42

How would you draw a line of best fit on a graph with error bars?

Answer 42

Ensure that the line of best fit passes through all of the error bars.

Question 43

How would you find the uncertainty in the gradient of a line of best fit?

Answer 43

Draw the steepest or shallowest line of worst fit, it still has to go through all the error bars. Then calculate the gradient of the lines of best and worst fit, the uncertainty is the difference between their gradients.

Question 44

How do you work out the uncertainty in the y-intercept of a line of best fit?

Answer 44

Draw a line of best and worst fit. the uncertainty in the y-intercept is: (best y-intercept)-(worst y-intercept)

Question 45

What is an order of magnitude?

Answer 45

Powers of ten which describe the size of an object/value, often used to compare different objects/values.

Question 46

What is the order of magnitude for the diameter of a nucleus?

Answer 46

10⁻¹⁵

Question 47

What is estimation?

Answer 47

A skill where approximate values are used to make comparisons or to check whether a calculated value is reasonable