Unit 1: Physical Quantities, Units and Measurement Techniques Flashcards
1
Q
What is the difference between accuracy and precision?
A
The accuracy of a measurement refers to how close it is to the true or accepted value while precision refers to how close they are to each other.
One important distinction between accuracy and precision is that accuracy can be determined by only one measurement, while precision must be determined with multiple measurements.
2
Q
In many cases, where precision is high and accuracy is low, _________(what does it imply?)
A
The fault can lie with the instrument.
For e.g. if a balance or a thermometer is not working correctly, they may consistently give inaccurate answers, resulting in high precision and low accuracy.
3
Q
What are the four cases of the degree of accuracy and precision?
A
- High accuracy, high precision
- Low accuracy, high precision
- High accuracy, low precision
- Low accuracy, low precision
4
Q
Why do we record to half the smallest division when taking a single reading from an instrument?
A
This accounts for human ability to visually estimate values between scale markings, improving precision without introducing excessive uncertainty.
Check the physics chat in ChatGPT if unsure
5
Q
Why do we record to the smallest division when taking measurements that involve an interval between two readings?
A
To prevent compounding uncertainties from both readings, ensuring the total uncertainty remains consistent with the scale of the instrument.
Check the physics chat in ChatGPT if unsure
6
Q
What happens to uncertainty when subtracting two readings in an interval measurement?
A
The uncertainties of both readings combine, doubling the total uncertainty.
7
Q
Why is recording to half the smallest division for interval measurements generally avoided?
A
It could misrepresent the precision by compounding the estimation errors of both readings, making the final result less reliable.
8
Q
When measuring an angle using a protractor, why does it involve an interval between two readings?
A
Because the angle is determined by the difference between two positions where the sides of the angle intersect the protractor’s scale.
9
Q
Why does measuring a length using a meter rule involve an interval between two readings?
A
Because you determine the length by taking the reading at the start point and the end point, then subtracting the two to find the interval (length).
10
Q
All physical quantities consist of ___________________.
A
a numerical magnitude and a unit
11
Q
Everything that is measurable can be measured by ________________.
A
Seven SI base units or by units derived from these base units.
12
Q
What are the seven base quantities?
A
Length, Mass, Time, Current, Temperature, Amount of Substance, Luminous intensity (luminous intensity is not tested)
13
Q
What are the base units of the seven base quantities?
A
Metre, kilogram, second, ampere, kelvin and mole
14
Q
What are the symbol of the seven base quantities?
A
m, kg, s, A, K, mol
15
Q
What is the way to remembering the seven base quantities?
A
Imagine a man that is very tall in height/plum (length) and he goes on a trampoline (mass) and flies up into the air (time), he hit the electric circuit and current (current) starts to flow through his body. The temperature (temperature) of his body goes up rapidly and substances (amount of substance) from his body starts to escape and rise into the air.
16
Q
What is the purpose of having the 7 SI units?
A
For communication (have a “common language” and conversion, consistency, reliability —>multiple readings will be reliable
17
Q
What are the two types of quantities?
A
Base unit and derived quantities
18
Q
Is current a base quantity? If so, provide me with its base unit and symbol.
A
Yes. Its base unit is ampere and its symbol is A
19
Q
Given the equation: current = charge (in coulumbs)/ time, derive the units for charge (in terms of SI base units).
A
SI unit of current is A
SI unit of time is s
So Charge = current x time
= A s or A.s
20
Q
What are the 4 derived units?
A
newton (N)
pascal (Pa)
joule (J)
watt (W)
21
Q
What are the four quantities of derived units?
A
Force
Pressure
Work done
Power
22
Q
What is the SI base units for force?
A
^ means to the power
kg m s^-2
23
Q
What is the SI base units of pressure?
A
^ means to the power
kg m^-1 s^-2
24
Q
What is the SI base units of work done?
A
^ means to the power
kg m^2 s^-2
25
What is the SI base units of power?
^ means to the power
kg m^2 s^-3
26
Prefixes are used with units in order to _______________.
increase or decrease the value that they represent.
27
All of the prefixes represent some factor of ___, and they can be used with ______________.
All of the prefixes represent some factor of 10, and they can be used with any of the SI base units.
28
What is the symbol of tera, giga, mega, kilo, deci, centi, milli, micro and nano?
T, G, M, k, d, c, m |u (combined—> can check one note) and n respectively
29
What is the number that you use to multiply the base by for tera, giga, mega, kilo, deci, centi, milli, micro and nano?
^ stands for to the power of
tera—> 1 x 10^12
giga—> 1 x 10^9
mega-> 1 x 10^6
milli—> 1 x 10^-3
micro->1 x 10^-6
nano—>1 x 10^-9
30
If a number does not have a decimal point and the right most digit is zero, then it is __________________.
If a number does not have a decimal point and the right most digit is zero, then it is unclear as to the number of s.f. it has.
31
The value 20cm can be interpreted as having ____________ because it happened to be exactly 20cm.
2.sf. (Nearest unit) because it happened to be exactly 20cm.
It can also be interpreted as having 1s.f. (Nearest ten) because its actual value was 18cm and was rounded off to nearest 1s.f.
32
What is a common number of significant numbers for all of these numbers?
123
12.3
1.23 x 10 to the power of 6
1.00
0.000103
123,000
three significant figures
33
What is the meaning of limits of accuracy?
To describe all the possible values that a rounded number could be
34
What is the limits of accuracy for the value 3?
Between 2 and 4
35
What is the limits of accuracy for the value 3.0?
Between 2.9 and 3.1
36
What is the limits of accuracy for the value of 3.00?
Between 2.99 and 3.01
37
How many significant figures does 3.0 have?
2
38
How many significant figures does 0.30 have?
2
39
How many significant figures does 3.0 x 10 to the power of 2 have?
2
40
How many significant figures does the value 3, 0.3 and 3 x 10 to the power of 2 have respectively?
1 significant figures for all of the values
41
How many significant figures does the value 3.00, 0.300, 3.00 x 10 to the power of 2 have?
3 significant figured for all of the values.
42
What is the limits of accuracy for the values 0.3, 0.30 and 0.300 respectively?
Between 0.2 and 0.4 for 0.3.
Between 0.29 and 0.31 for 0.30
Between 0.299 and 0.301 for 0.300
43
What is the limits of accuracy for the values 3 x 10 to the power of 2. 3.0 x 10 to the power of 2 and 3.00 x 10 to the power of 2?
Between 200 and 400 for 3 x 10 to the power of 2
Between 290 and 310 for 3.0 x 10 to the power of 2
Between 299 and 301 for 3.00 x 10 to the power of 2
44
State the number of s.f. figures for 10.0340.
6
Just follow this simple rule:
Any zero before a non-zero number, you don’t count
Zero after a non-zero number, you count (trailing zero)
45
State the number of s.f. for 0.0340
3s.f.
46
Round off the following number to 1s.f. 10.0340
A:1
B: 1.0
C: 10
D: 10.0
C
10 can be either 1 s.f. Or 2 s.f.
47
The digital calibers are used to measure the _____ and ______ diameters of an object accurately.
The object is gripped gently using the jaws of the ______ . The depth bar can be used to measure the _____ of an object.
The digital calibers are used to measure the internal and external diameters of an object accurately.
The object is gripped gently using the jaws of the caliper . The depth bar can be used to measure the depth of an object.
48
What are the steps to measuring the dimension of the object?
1. Close the jaws of the calibers with no object in between.
2. Press the origin button and reopen the jaws.
3. The object is placed between the external or internal jaws of the calipers depending on the type of measurement.
Make sure you remember this. It is important.
49
A digital calipers is precise to ______ or ________. Why precision of an instrument?
It is precise to 0.001cm or 0.01mm.
A digital caliper cannot inherently guarantee accuracy because accuracy depends on how well the caliper is calibrated.
However, it can guarantee precision, as this is built into its design (e.g., the resolution of the digital display).
50
How many d.p. should you record to in terms of mm for digital vernier calipers?
2 d.p. in mm
51
How many d.p. should you record to in terms of mm for digital micrometer screw gauge?
3d.p. in mm
52
What is the measuring range for measuring tape?
0 to several metres
53
What is the measuring range for metre ruler?
0 to one metre
54
What is the measuring range for analogue vernier calipers?
0 to 15cm
55
What is the measuring range for analogue micrometer screw gauge?
0 to 2.5cm
56
What is the measuring range for digital calipers?
0 to 15cm
57
What is the measuring range for digital micrometer screw gauge?
0 to 2.5cm
58
What is the smallest division for measuring tape? Record the measurement to ____________.
The smallest division for measuring tape is 0.1cm or 1mm.
We record the measurement to plus minus 0.5mm ( plus minus 0.05cm
59
What is the smallest division for metre ruler? Record the measurement to ___________.
The smallest division for metre ruler is 0.1cm or 1mm. Measurements using after ruler should be recorded to half the smallest division, which is plus minus 0.05cm.
60
Why do we record measurements to half the smallest division for a metre ruler?
To account for estimation between the smallest markings on the scale.
61
What is the smallest division of an analogue vernier caliper?
0.01cm (0.1mm)
62
How should measurements using an analogue vernier caliper be recorded?
To half the smallest division, which is plus minus 0.005cm
63
Why do we record measurements to half the smallest division for analogue vernier caliper?
To account for possible estimation when aligning the mains scale and vernier scale.
64
What is the smallest division of an analogue micrometer screw gauge?
0.01 mm (0.001cm)
65
How should measurements using an analogue micrometer screw gauge be recorded?
To half the smallest division, which is plus minus 0.005mm (0.0005cm)
66
Why do we record measurements to half the smallest division for analogue micrometer screw gauges?
To account for estimation between the thimble scale markings.
67
What is the smallest division of a digital caliper?
0.01mm (0.001cm)
68
How should measurements using a digital caliper be recorded?
To the smallest division shown on the display, which is plus minus 0.01mm (0.001cm)
69
Why don’t we estimate half the smallest division for digital calipers?
Digital instruments directly display the smallest division without requiring manual estimation.
70
What is the smallest division of a digital micrometer screw gauge?
0.001mm (0.0001cm)
71
How should measurements using a digital micrometer screw gauge be recorded?
To the smallest division shown on the display, which is $0.001 mm (0.0001 cm).
72
Why don’t we estimate half the smallest division for digital micrometer screw gauges?
Digital instruments eliminate estimation by directly display the reading.
73
Go and take a look at the diagram of the digital calipers in one note under unit 1. Take a photo of it, upload to notability and erase it using the eraser to test yourself the labelling.
74
Go and take a look at the diagram of the digital micrometer screw gauge in one note under unit 1. Take a photo of it, upload to notability and erase it using the eraser to test yourself the labelling.
75
The digital micrometer screw gauges is used to measure objects that are _______________.
The digital micrometer screw gauges is used to measure objects that are too small to be measured using the digital calipers.
76
What are the steps to measuring the dimension of the object using a digital micrometer screw gauge?
1. Turn the ratchet until the spindle is in contact with the anvil with no object in between.
2. Press the rezero button and reopen the spindle.
3. The object is placed between the anvil and spindle.
4. The ratchet is turned until clicks are heard.
5. This indicates that the hold is now of the correct pressure and any further movement of the spindle will compress the object.
77
A digital calipers is precise to _______ or __________.
A digital calipers is precise to 0.001cm or 0.01mm.
78
A digital micrometer screw gauge is precise up to ___________ or ____________.
A digital micrometer screw gauge is precise up to 0.0001cm or 0.001mm.
79
How many d.p. in mm do you record for the measurements on your digital micrometer screw gauge?
3
80
What is the definition of systematic errors?
Systematic errors result in all readings or measurements being always above or always below the true value by a fixed amount.
81
Errors have to do with accuracy and precision. Is this true or false.
False. Errors have nothing to do with accuracy and precision.
82
Can errors be eliminated?
The only error that can be eliminated is systematic error.
83
Can a systematic error be eliminated? If so, how and when? If not, why?
A systematic error can be eliminated only if the source of the error is known and account for. It cannot be eliminated by repeating measurements and averaging them.
84
What are two examples of systematic errors?
Not accounting for zero error in a measurement.
An instrument has a zero error if the scale reading is non-zero before a reading is taken. Instruments should be checked for zero error and the zero error must be accounted for in the measurement.
Not accounting for background radiation when measuring activity of a radioactive source.
85
What is the definition of random errors?
Random errors result in readings or measurements being scattered about a mean value. These errors have equal chance of being positive or negative.
86
Random errors may be reduced but not __________.
Random errors may be reduced but not eliminated.
87
Random errors may be reduced by
______________________ and
_______________________________.
Random errors may be reduced by repeating a measurement and averaging and plotting a graph and drawings a line of best fit for the plotted points.
88
What are two examples of random errors?
Fluctuation in the count-rate of a radioactive decay and variation in the diameter of a piece of wire.
89
One way to measure a fixed interval of time is to use a ______________.
Pendulum.
90
As the pendulum swings, the movement from position A to B and back to A again is called an ______________.
Oscillation.
91
The time taken to make one complete oscillation is called a ___________, usually represented by the symbol _____.
The time taken to make one complete oscillation is called a period, usually represented by the symbol T.
92
We usually do not measure the _______ directly, but measure the time taken for multiple osci______; then; dividing that time by the number of osci______ to determine the ___________.
We usually do not measure the period directly, but measure the time taken for multiple oscillations; then; dividing that time by the number of oscillations to determine the period.
93
The period T is dependent on the ________ ____ of the pendulum. Formula: ____________
The period T is dependent on the length L of the pendulum. [T = 2 pi square root of (L/g)
94
What are scalars and vectors?
Scalars are quantities that are fully described by a magnitude alone.
Vectors are quantities that are fully described by both a magnitude and a direction.
95
Vectors help us understand and analyse concepts such as _______ and ________
motion and forces
96
What are some examples of scalar quantities? (Try to give 9 examples)
Distance, speed, time, mass, area, volume, energy, work done, and power
97
What are some examples of vector quantities? (Try to give 5 examples)
Some examples of vector quantities are displacement, velocity, acceleration, force, and momentum.
98
Is density a scalar or vector quantity?
Density is a scalar quantity because it only has magnitude and no direction; it is calculated by dividing mass (a scalar) by volume (also a scalar), so it inherits the scalar nature of its components.
This means that density as a whole is scalar quantity.
99
Is weight a scalar or a vector quantity?
Yes, weight is considered a vector quantity because it has both magnitude and direction, as it represents the gravitational force acting on an object, which always pulls downwards towards the center of the Earth; therefore, it has a defined direction alongside its magnitude.
Key points about weight as a vector:
Definition: Weight is the force exerted on an object due to gravity.
Magnitude: Represents the numerical value of the weight.
Direction: Always points downwards towards the center of the Earth.
100
Can speed be negative?
No, a body's speed can never be negative because speed is a scalar quantity. Q.
101
Can velocity be negative?
Yes, velocity can be negative because it is a vector quantity, meaning it includes both magnitude (speed) and direction; a negative velocity simply indicates motion in the opposite direction of what is defined as positive in your chosen coordinate system.
Key points about negative velocity:
Direction matters:
If you define "right" as positive, then movement to the left would be considered negative velocity.
Displacement is key:
A negative velocity means the displacement (change in position) is in the negative direction.
Speed is always positive:
While velocity can be negative, speed (the absolute value of velocity) is always positive.
102
Negative velocity is only meaningful in some situations. What are they?
In the cases of linear motion which is in one-dimensional motion, such as along a straight line, negative velocity simply conveys information about the direction of motion relative to a chosen reference, making it meaningful whenever direction matters.
103
The addition of scalar quantities is done by ___________________. For instance, 4.0kg plus 5.0kg will always give ________ (mass is a scalar quantity)
The addition of scalar quantities is done by arithmetic addition. For instance, 4.0kg plus 5.0kg will always give 9.0 kg (mass is a scalar quantity
104
Any vector can be represented by an _________.
Any vector can be represented by an arrow.
105
The length of the arrow represents the _______ of the vector.
The direction of the arrow represents the _______ of the vector.
The length of the arrow represents the magnitude of the vector.
The direction of the arrow represents the direction of the vector.
106
How does the addition of parallel vectors work?
Provide your explanation using this simple example:
a force of 4.0N and another force of 5.0N...
A force of 4.0N and another force of 5.0N can give a range of answers from 1.0N to 9.0N, depending on the direction of the forces.
If the forces are acting in the same direction, the resultant force will be equal to 4.0 + 5.0 = 9.0N to the right
If the forces are acting in opposite directions, the resultant force = 5.0 -4.0 = 1.0N to the left.
107
What can you do if you want to add vectors that are at an angle to each other (i.e. non-parallel vectors)?
For vectors at an angle to each other (i.e. non-parallel vectors), addition can be done using the vector the vector triangle method (also known as head-to-tail method) or the parallelogram method.
108
What are the steps to the vector triangle method?
Step 1:
Identify all vectors
Write in the respective information for vector A, B and the resultant vector in a table and tick if the magnitude or/and the direction is given.
Step 2: Do a simple sketch of the vector diagram. If necessary.
Step 3:
Choose an appropriate scale. Scale should be chosen such that the vector diagram can occupy as large a space as possible, to ensure greater accuracy.
Step 4:
In order to complete the vector diagram,
Start with A,B then C.
A
Draw all vectors that have both magnitude and direction.
B
Construct vectors with only known direction, leaving a long dotted line as the magnitude. If non-applicable, proceed to step C.
C
For vectors with only known magnitude, use a compass to intersect with the dotted line.
Step 4: Draw in vector 1, to scale, and in the correct direction.
Step 5: Draw in vector 2, ensuring the tail of vector 2 is placed at the head of vector 1 (head to tail)
Step 6: Resultant vector joins the starting point (tail) of vector 1 to the ending point (head)
The magnitude of the resultant vector can be found by measuring its length in the scale diagram, or using trigonometry (e.g. Pythagoras' Theorem in the case of right-angle triangles, or Cosine Rule (can also use Pythagoras' Theorem to check your answer).
Direction of the resultant vector can be found by indicating an angle, shown by theta, on the scale diagram and measuring it, or by using trigonometry (e.g. sine rule).
109
How does the parallelogram method work? (although it is more tedious and not recommended)
Two vectors acting at a point are represented by the sides of a parallelogram drawn from that point. Their resultant is represented by the diagonal which passes through that point of the parallelogram. Note that vector addition is commutative, i.e. A+B = B+ A
110
What is the meaning of the resultant vector?
Resultant vector is the answer to the addition of vectors.
111
What symbol is the change in velocity represented as?
a triangle
112
How can the change in velocity be obtained?
Final vector - initial vector
113
A motor boat heads east with an initial velocity of 5.0ms to the power of -1 for s. It then travels with an initial final velocity of 5.6ms to the power of -1 for S at a bearing 027 degrees. Determine the change in velocity of the boat.
So in this case you can start with the final velocity if you want since both final and initial velocity have both magnitude and direction. Since you need to find the change in velocity of the boat, you will have to subtract the initial velocity from the final velocity and the initial velocity has to be changed into negative which is basically the opposite direction.
Check one note unit 1 pg 12
114
How many d.p. in mm are you supposed to state your answer to for digital vernier calipers?
2 d.p. In mm
115
How many d.p. in mm are you supposed to state your answer to for digital micrometer screw gauge?
3 d.p. In mm
116
What is the meaning of bearing?
Bearing is the angle from the north in the clockwise direction.
For e.g. point B is at a bearing 015 degrees from Point A it means that A is the north and B is 15 degrees from the north direction
117
What is the story to remember which instruments need to be recorded to the smallest division?
Here’s how your **crazy exaggerated story** works:
1️⃣ **A crocodile is walking on a giant measuring tape that stretches from Earth to Mars.** 🌍🚀📏
- **(Metre rule / Measuring tape → Read to the smallest division!)**
2️⃣ **It’s holding a vernier calipers in its mouth, clamping down on it like a pro!** 🐊📏
- **(Vernier calipers → Read to the smallest division!)**
3️⃣ **Its legs are as tiny as an ant’s, so we need a micrometer screw gauge to measure them!** 🐜🔬
- **(Micrometer screw gauge → Read to the smallest division!)**
4️⃣ **Suddenly, the crocodile starts running and accidentally steps on an electronic balance!** ⚖️💨
- **(Electronic balance → Read to the smallest division!)**
5️⃣ **It keeps falling down, down, down… but a Newton meter catches him in mid-air!** 💪🔩
- **(Newton meter → Read to the smallest division!)**
6️⃣ **The Newton meter acts like a vine, and the crocodile swings around wildly in circles—forming a protractor shape!** 🔄🦎📐
- **(Protractor → Read to the smallest division!)**
🔥 **Key Takeaway:**
This **crazy mental movie** locks in the idea that all these instruments must be **read to the smallest division!** 🎯
118
What is the story to remember which instruments need to be recorded to half the smallest division?
Now, let's add the **Crazy Lab (Half the Smallest Division) Room**! 🤯
**💥 The crocodile crashes into a science lab!** 🧪💨
7️⃣ **It lands inside a giant measuring cylinder filled with bubbling green liquid!** 🧪🐊
- **(Measuring cylinder → Read to half the smallest division!)**
8️⃣ **The impact launches a spring balance into the air, and it gets tangled in the crocodile’s tail!** 🌀🐊
- **(Spring balance → Read to half the smallest division!)**
9️⃣ **Lightning strikes, and a milliammeter + ammeter start sparking!** ⚡💡🔢
- **(Milliammeter & Ammeter → Read to half the smallest division!)**
🔟 **Suddenly, a giant voltmeter appears, and the crocodile gets zapped into an old-school thermometer!** 🌡️⚡🐊
- **(Voltmeter + Liquid-in-glass thermometer → Read to half the smallest division!)**
119
What do you record the digital vernier and digital micrometer screw gauge to?
Finally, the **Digital Command Center** 🤖
**⚡ The crocodile lands in a futuristic digital lab!** 🚀
11️⃣ **A digital vernier caliper scans it instantly!** 🦾📏
- **(Digital Vernier → Read directly from display!)**
12️⃣ **A digital micrometer screw gauge zooms in to analyze its scales!** 🔍🐊
- **(Digital Micrometer → Read directly from display!)**
120
What is the number that you need to multiply the base by for tera?
1 x 10 to the power of 12
121
What is the number that you need to multiply the base by for giga?
1 x 10 to the power of 9
122
What is the number that you need to multiply the base by for mega?
1 x 10 to the power of 6
123
What is the number that you need to multiply the base by for kilo?
1 x 10 to the power of 3
124
What is the number that you need to multiply the base by for deci?
1 x 10 to the power of -1
125
What is the number that you need to multiply the base by for centi?
1 x 10 to the power of -2
126
What is the number that you need to multiply the base by for milli?
1 x 10 to the power of -3
127
What is the number that you need to multiply the base by for micro?
1 x 10 to the power of -6
128
What is the number that you need to multiply the base by for nano?
1 x 10 to the power of -9
129
Convert to the stated units and quote answers in standard form:
0.50 µs = _________s.
0.50 µs = (0.50 µs/ 1) x (10 to the power of -6 s)/ 1 µs)
and NOT 1s/ 10 to the power of -6 µs
µs is already small enough don't make it smaller by putting 10 to the power of -6
