Physical Quantities, Units and Measurements

Question 1

what are the 6 base quantities? (and SI unit)

Answer 1

1) length: metre (m)
2) mass: kilogram (kg)
3) time: second (s)
4) electric current: ampere (A)
5) thermodynamic temperature: kelvin (K)
6) amount of substance: mole (mol)

Question 2

what does tera- (T) represent?

Answer 2

10¹²

Question 3

what does giga- (G) represent?

Answer 3

10⁹

Question 4

what does mega- (M) represent?

Answer 4

10⁶

Question 5

what does kilo- (k) represent?

Answer 5

10³

Question 6

what does deci- (d) represent?

Answer 6

10⁻¹

Question 7

what does centi- (c) represent?

Answer 7

10⁻²

Question 8

what does micro- (µ) represent?

Answer 8

10⁻⁶

Question 9

what does milli- (m) represent?

Answer 9

10⁻³

Question 10

what does nano- (n) represent?

Answer 10

10⁻⁹

Question 11

what instrument should be used to measure a lengths of several metres?

Answer 11

tape measure

Question 12

what instrument should be used to measure lengths ranging from several centimetres to 1 metre?

Answer 12

metre rule

Question 13

what instrument should be used to measure lengths ranging from 1 to 15 centimetres?

Answer 13

digital calipers

Question 14

what instrument should be used to measure lengths less than 2.5 centimetres?

Answer 14

digital micrometre screw gauge

Question 15

what is the precision of a tape measure?

Answer 15

0.1cm (1mm)

Question 16

what is the precision of a metre rule?

Answer 16

0.1cm (1mm)

Question 17

what is the precision of a digital calipers?

Answer 17

0.001cm (0.01mm)

*round to 0.01cm (0.1mm) to account for significant sources of error

Question 18

what is the precision of a digital micrometre screw gauge?

Answer 18

0.0001cm (0.001mm)

*round to 0.001cm (0.01mm) to account for significant sources of error

Question 19

how do you prevent parallax errors when reading from a metre rule?

Answer 19

position your eye vertically above the scale such that your line of sight is perpendicular to the rule marking

*results from wrong positioning of the eye

Question 20

how do you prevent zero errors when reading from a metre rule?

Answer 20

• measure from another point and subtract it from the final reading rather than starting at 0.0cm
• take several readings and calculate the average to minimise errors

*results from wear-and-tear

Question 21

what are the 7 main parts of the digital calipers?

Answer 21

1) inside jaw
2) outside jaw
3) locking screw
4) digital display
5) zero button
6) scale
7) tail

Question 22

what is the purpose of the inside jaws of a digital calipers?

Answer 22

used to measure the internal diameter of an object

Question 23

what is the purpose of the outside jaws of a digital calipers?

Answer 23

used to measure the external diameter or width of an object

Question 24

what is the purpose of the locking screw of a digital calipers?

Answer 24

used to ensure that the jaws do no move apart after measuring

Question 25

what is the purpose of the digital display of a digital calipers?

Answer 25

used to show the numeric value (i.e. the length)

*precision will show 0.001cm (0.01mm), round to 0.01cm (0.1mm)

Question 26

what is the purpose of the zero button of a digital calipers?

Answer 26

used to reset the displayed length back to zero (prevents zero error)

Question 27

what is the purpose of the tail of a digital calipers?

Answer 27

used to measure the depth of an object

Question 28

why is a digital calipers used rather than a vernier calipers?

Answer 28

• zero errors can be removed by pressing the zero button when the inside/outside jaws are touching each other so that the displayed length is reset to zero
• digital calipers has one more decimal place on the display (in mm)

Question 29

what are 2 advantages of digital calipers over metre rules?

Answer 29

• better precision
• can be used to measure internal/external diameters or widths and depths of objects (can measure two extreme ends of a circular object accurately)

Question 30

what are the 7 main parts of the analogue micrometer screw gauge?

Answer 30

1) anvil
2) spindle
3) main scale
4) thimble scale
5) thimble
6) datum line
7) ratchet

Question 31

what are the 7 main parts of the digital micrometer screw gauge?

Answer 31

1) anvil
2) spindle
3) digital display
4) zero button
5) scale
6) thimble
7) ratchet

Question 32

what is the purpose of the anvil and spindle of a digital micrometer screw gauge?

Answer 32

used to measure the diameter of an object

Question 33

what is the purpose of the digital display of a digital micrometer screw gauge?

Answer 33

used to show the numeric value (i.e. the length)

*precision will show 0.0001cm (0.001mm), round to 0.001cm (0.01mm)

Question 34

what is the purpose of the zero button of a digital micrometer screw gauge?

Answer 34

used to reset the displayed length back to zero (prevents zero error)

Question 35

what is the purpose of the ratchet of a digital micrometer screw gauge?

Answer 35

-can be turned to adjust the spindle so that the spindle is in contact with the object
- can prevent overtightening of the digital micrometer screw gauge, otherwise the object may be damaged and the reading will be lower than the theoretical value

Question 36

why is a digital micrometer screw gauge used rather than an analogue micrometer screw gauge?

Answer 36

• zero errors can be removed by pressing the zero button when the anvil and spindle are touching each other so that the displayed length is reset to zero
• digital micrometer screw gauge has one more decimal place on the display (in mm)

Question 37

how could you obtain a good estimate of the circumference of a tree using instruments to measure lengths?

Answer 37

• use a tape measure and wrap it around the trunk to take the circumference
• do so for 2 points long the trunk
• take the average of at least 3 sets of readings