M2 Units, Measurement and Errors Flashcards

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1
Q

define quantity

A

implies a measurement of something and its units

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2
Q

what are the six basic quantities and their unit

A
Mass - kg
Time - s
Current - A
Temperature - K
Length - m
Amount of substance - mol
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3
Q

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

A

-1

d

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4
Q

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

A

-2

c

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5
Q

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

A

-3

m

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6
Q

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

A

-6

weird u

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7
Q

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

A

-9

n

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8
Q

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

A

-12

p

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9
Q

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

A

-15

f

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10
Q

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

A

3

k

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11
Q

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

A

6

M

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12
Q

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

A

9

G

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13
Q

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

A

12

T

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14
Q

what’s the difference between accuracy and precision

A

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

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15
Q

how do you measure off a vernier calliper

A

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

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16
Q

how do you measure off a micrometre screw gauge

A

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

17
Q

what is more accurate, a vernier calliper or a micrometre

A

micrometer

18
Q

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

A

+ or - the smallest scale division

19
Q

what is the error or uncertainty of a metre stick

A

+ or - 1mm

20
Q

what is the error or uncertainty of a vernier calliper

A

+ or - 0.1mm

21
Q

what is the error or uncertainty of a micrometer screw gauge

A

+ or - 0.01 mm

22
Q

how do you work out percentage error

A

(error / measurement) X 100

23
Q

how do you combine errors when adding or subtracting quantities

A

add errors

24
Q

how do you combine errors when multiplying or dividing quantities

A

add percentage errors

25
Q

how do you combine errors when raising to a power

A

multiply the percentage error by the power

26
Q

what is a zero error

A

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

27
Q

what is a systematic error

A

caused by inaccuracy in the apparatus or its

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

28
Q

what is a random error

A

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.

29
Q

what’s an absolute uncertainty

A

the total uncertainty of the measurement

30
Q

what’s a percentage uncertainty

A

the uncertainty as a percentage of the measurement

31
Q

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

percentage error in the measurement?

A

% 𝐄𝐫𝐫𝐨𝐫 =
𝟎.𝟎𝟏/𝟓.𝟐𝟓
× 𝟏𝟎𝟎 = 𝟎. 𝟐%

32
Q

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

A

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

33
Q

How do you work out the gradient

A

∆y / ∆x

34
Q

equation of a straight line

A

y = mx + c

35
Q

estimate:

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

A

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

36
Q

what is meant by homogeneity of units

A

the units in any equation must be equal on both sides

37
Q

what is pd in base units

A

kgm^2s^-3A^-1