[D] TOPIC 1: MEASUREMENT

Question 1

7 Base Quantities

Answer 1

mass, kg
length, m
time, s
temperature, K
electric current, A
amount of substance, mol
luminous intensity, cd

Question 2

Prefixes

Answer 2

Tera 10^12
Giga 10^9-6
Mega 10^6
kilo 10^3
deci 10^-1
centi 10^-2
milli 10^-3
micro 10^-6
nano 10^-9
pico 10^-12

Question 3

Mass of a bus

Answer 3

12000kg / 15000kg

Question 4

Mass of a car

Answer 4

1200kg / 1500kg

Question 5

Random error vs Systematic error

Answer 5

Measured values are scattered about the true value with no fixed pattern

Measured values are consistently larger of consistently smaller than the true value

Question 6

Reducing error of
1. random error
2. systematic error

Answer 6

1. reduce by averaging (cannot be eliminated)
2. reduce by correct laboratory practice (can be eliminated)

Question 7

Accuracy VS Precision (of readings & instrument)

Answer 7

Accuracy: how close the measured value is to the true value

Precision (of a set of readings): how close the measured values are to each other

Precision (of an instrument): the size of the smallest division

Question 8

d.p. / s.f. for uncertainty, Δx

Answer 8

For addition/subtraction, follow least d.p. rule
For multiplication/division, follow least s.f. rule

On its own (aka fractional or percentage uncertainty): 2sf

When provided with its value (aka x ± Δx): 1sf, then x take same dp as uncertainty

Question 9

Calculating uncertainty using 2 methods

Answer 9

“Max-Min” Method:
Δx = 1/2 [z(max) - z(min)]

Error Propagation Method:
z = m(x1) + x2 - n(x3)
Δz = m(Δx1) + Δx2 + n(Δx3)

z = [k(A^n)B]/[q(C^m)]
Δz/z = Δk/k + n(ΔA/A) + ΔB/B + Δq/q + m(ΔC/C)

Question 10

Vector diagram: Change in X

Answer 10

X(final) - X(initial)

Question 11

Vector diagram: X relative to Y

Answer 11

X - Y