M2 Units, Measurement and Errors

Question 1

define quantity

Answer 1

implies a measurement of something and its units

Question 2

what are the six basic quantities and their unit

Answer 2

Mass - kg
Time - s
Current - A
Temperature - K
Length - m
Amount of substance - mol

Question 3

what is deci to the power of and what’s its symbol

Answer 3

-1

d

Question 4

what is centi to the power of and what’s its symbol

Answer 4

-2

c

Question 5

what is milli to the power of and what’s its symbol

Answer 5

-3

m

Question 6

what is micro to the power of and what’s its symbol

Answer 6

-6

weird u

Question 7

what is nano to the power of and what’s its symbol

Answer 7

-9

n

Question 8

what is pico to the power of and what’s its symbol

Answer 8

-12

p

Question 9

what is femto to the power of and what’s its symbol

Answer 9

-15

f

Question 10

what is kilo to the power of and what’s its symbol

Answer 10

3

k

Question 11

what is mega to the power of and what’s its symbol

Answer 11

6

M

Question 12

what is giga to the power of and what’s its symbol

Answer 12

9

G

Question 13

what is tera to the power of and what’s its symbol

Answer 13

12

T

Question 14

what’s the difference between accuracy and precision

Answer 14

accuracy describes the difference between the measurement and the actual value whereas precision describes how close to each other repeated measurements are

Question 15

how do you measure off a vernier calliper

Answer 15

look at the zero of a vernier scale and read where this comes on the main scale, estimating the figure for tenths of a millimetre
look along the vernier scale to see what vernier division coincides with one of the divisions on the main scale - this gives the correct figure for tenths of a millimetre

Question 16

how do you measure off a micrometre screw gauge

Answer 16

read the main scale, estimating the figure for tenths of a millimetre
read the scale on the sleeve

Question 17

what is more accurate, a vernier calliper or a micrometre

Answer 17

micrometer

Question 18

the possible error associated with an instrument is always taken as…

Answer 18

+ or - the smallest scale division

Question 19

what is the error or uncertainty of a metre stick

Answer 19

+ or - 1mm

Question 20

what is the error or uncertainty of a vernier calliper

Answer 20

+ or - 0.1mm

Question 21

what is the error or uncertainty of a micrometer screw gauge

Answer 21

+ or - 0.01 mm

Question 22

how do you work out percentage error

Answer 22

(error / measurement) X 100

Question 23

how do you combine errors when adding or subtracting quantities

Answer 23

add errors

Question 24

how do you combine errors when multiplying or dividing quantities

Answer 24

add percentage errors

Question 25

how do you combine errors when raising to a power

Answer 25

multiply the percentage error by the power

Question 26

what is a zero error

Answer 26

caused when an instrument is not properly calibrated so it gives a non-zero value when the true value is zero

Question 27

what is a systematic error

Answer 27

caused by inaccuracy in the apparatus or its

use by the person conducting the experiment. Shifts all the measurements in the same direction.

Question 28

what is a random error

Answer 28

causes measurements to be scattered above

and below the true value when repeated. Better results can be obtained by finding a mean value of several results.

Question 29

what’s an absolute uncertainty

Answer 29

the total uncertainty of the measurement

Question 30

what’s a percentage uncertainty

Answer 30

the uncertainty as a percentage of the measurement

Question 31

If I measure the time as 5.25 ± 0.01 s then what is the

percentage error in the measurement?

Answer 31

% 𝐄𝐫𝐫𝐨𝐫 =
𝟎.𝟎𝟏/𝟓.𝟐𝟓
× 𝟏𝟎𝟎 = 𝟎. 𝟐%

Question 32

If the extension of a spring is (5.1 ± 0.3 cm) – (2.0 ± 0.1 cm) then what is the extension?

Answer 32

(5.1 – 2.0) ± (0.3 + 0.1) cm = 3.1 ± 0.4 s

Question 33

How do you work out the gradient

Answer 33

∆y / ∆x

Question 34

equation of a straight line

Answer 34

y = mx + c

Question 35

estimate:

i) mass of a person
ii) mass of a car
iii) height of a man
iv) walking speed

Answer 35

i) 70kg
ii) 1500kg
iii) 1.8 m
iv) 1.5ms^-1

Question 36

what is meant by homogeneity of units

Answer 36

the units in any equation must be equal on both sides

Question 37

what is pd in base units

Answer 37

kgm^2s^-3A^-1