Measurements Flashcards
(232 cards)
1
Q
What are derived quantities?
A
Quantities that are obtained by combination of fundamental quantities.
2
Q
What are derived units?
A
The units of derived quantities.
3
Q
Give examples of derived quantities and their units.
A
Area (m²)
4
Q
How is the unit of area derived?
A
It is a product of length and breadth (m x m = m²).
5
Q
How is the unit of volume derived?
A
It is a product of length
6
Q
Why do units used in industry and business sometimes differ from those used in the laboratory?
A
Because in these areas
7
Q
Give an example of a unit used for power in industry.
A
Horsepower (hp).
8
Q
How much is one horsepower equal to?
A
0.746 kilowatts.
9
Q
What unit is used to measure oil in oil industries?
A
Barrel.
10
Q
Approximately how many liters are in a barrel of oil?
A
Between 120 and 159 liters.
11
Q
What unit is used for measuring the area of land?
A
Hectare (ha).
12
Q
How many square meters are in a hectare?
A
10
13
Q
Are measurements in physics perfectly precise?
A
No.
14
Q
What should you note about a measuring instrument when taking measurements?
A
The reading accuracy.
15
Q
How should measurements be specified?
A
In the correct number of significant figures.
16
Q
What is good practice when giving the result of a measurement?
A
To state the precision or estimated uncertainty.
17
Q
What does the notation “51.3 ± 0.1 cm” mean?
A
That the length is probably between 51.2 and 51.4 cm.
18
Q
What are significant figures?
A
The reliably known digits in a number.
19
Q
How are significant figures usually determined?
A
As all figures from the first non-zero digit to the last non-zero digit
20
Q
How many significant figures are in 51.35?
A
Four.
21
Q
How many significant figures are in 0.053 cm?
A
Two.
22
Q
What instruments are used to measure length in a secondary school physics laboratory?
A
Metre rule
23
Q
What are the graduations on a metre rule?
A
Centimeters and millimeters.
24
Q
What is the smallest graduation of a metre rule?
A
1 mm or 0.1 cm.
25
What is the reading accuracy of a metre rule?
0.1 cm.
26
What is the estimated uncertainty when measuring with a metre rule?
0.05 cm.
27
How can a length measurement with a metre rule be recorded?
As 21.55 ± 0.05 cm.
28
What precaution is necessary when measuring with a metre rule?
To avoid parallax error by looking vertically downwards on the markings.
29
What are steel tapes graduated in metres used for?
Measuring large distances like the length or width of a football field.
30
What is the purpose of vernier calipers?
To measure lengths more accurately than a metre rule.
31
What is the accuracy of vernier calipers?
To the nearest 0.1 mm.
32
Give examples of what vernier calipers can measure.
Thickness of a metre rule
33
What are the two scales on a vernier caliper?
The main scale and the vernier scale.
34
What does the vernier scale do?
It slides on the main scale and measures a fraction of the smallest division on the main scale.
35
What are the graduations on the main scale of a vernier caliper?
Centimeters and millimeters.
36
How is the vernier scale constructed?
By dividing a 9 mm length into 10 equal intervals.
37
What is the length of each vernier division?
0.9 mm or 0.09 cm.
38
What is the difference in length between a vernier scale division and a main scale division?
0.1 mm or 0.01 cm.
39
How is the total reading of a length obtained using a vernier caliper?
By adding the readings on both the main and vernier scales.
40
How do you record the reading on the main scale?
By noting the reading immediately preceding the zero mark on the vernier scale.
41
How do you record the reading on the vernier scale?
By noting the graduation on the vernier scale that aligns most directly with a graduation on the main scale.
42
What does the vernier scale reading give you?
The decimal place in millimeters or the second decimal place in centimeters.
43
What is the accuracy of vernier calipers?
0.01 cm.
44
What precaution should be taken when using a vernier caliper?
Always note if it has any zero error.
45
How do you check for zero error in a vernier caliper?
By setting the zeros of the main scale and the vernier scale to coincide.
46
What do you do if the zeros of the main scale and vernier scale do not coincide?
Note the difference as the 'zero error'.
47
How do you correct for zero error in subsequent readings?
Add or subtract the zero error as appropriate.
48
For what type of measurements is a micrometer screw gauge used?
Accurate measurements of small lengths.
49
Give examples of measurements taken with a micrometer screw gauge.
Diameter of a wire
50
What is the accuracy of a micrometer screw gauge?
0.001 cm.
51
What should be done before making measurements with a screw gauge?
Check for zero error.
52
What are the two scales on a micrometer screw gauge?
A main scale and a vernier scale.
53
What are the graduations on the main scale of a micrometer screw gauge?
Millimeters.
54
How many equal divisions are on the circular vernier scale of a micrometer screw gauge?
50
55
How far does the screw head move along the main scale when turned once?
0.5 mm.
56
What is the value of one division on the vernier scale of a micrometer screw gauge?
0.01 mm.
57
How can you obtain the volume of a rectangular block?
By measuring its length (l)
58
How can you obtain the volume of an irregular solid?
By immersing it completely in a measuring cylinder containing a liquid in which the solid is insoluble. The volume of the liquid displaced gives the volume of the solid.
59
How do you measure the volume of a sphere?
By measuring its diameter (d) with a micrometer screw gauge and using the formula V = (4/3)πr³
60
How do you measure the volume of a cylindrical wire?
By measuring the length (l) with a metre rule and the diameter (d) with a micrometer screw gauge and using the formula Volume = πr²l or π(d²/4)l.
61
What instruments can be used to measure the volume of a liquid?
A measuring cylinder
62
Where is the correct liquid level read in a graduated glass container?
At the bottom of the meniscus (or curved surface of the liquid).
63
How is mass defined?
As the quantity of matter or 'stuff' contained in a body.
64
How is weight defined?
As the force or pull with which the earth attracts the body towards the centre of the earth.
65
What instrument is used to measure mass?
A balance.
66
Name types of balances.
Beam or chemical balance
67
How is the mass of a body usually measured?
By comparing it with 'standard' masses.
68
How do you measure with a beam balance?
Place the object on the left-hand scale pan and standard masses on the right-hand scale pan.
69
What should the beam of the balance do when raised for weighing?
Swing freely about a pivot in the centre of the beam.
70
How do you know when the masses in the two scale pans are equal?
When the pointer swings equal number of divisions on each side of the central mark or the pointer balances on the central mark of the scale.
71
How do you obtain the mass of the object?
By adding the standard masses on the right scale pan.
72
On what principle does the beam balance work?
The principle of moments.
73
What is the reading accuracy of a beam balance?
Up to 0.001 grams.
74
What should you use for picking up standard masses when using a beam balance?
Forceps.
75
What should you do to objects before placing them on the scale pan?
Wipe them dry.
76
What should you do with hot objects before weighing them?
Allow them to cool.
77
When should you avoid adding or removing known masses from the scale pan?
While the beam is in the raised position.
78
What instrument is used to find the weight of an object?
A spring balance.
79
What law is the spring balance calibrated using?
Hooke's law.
80
What does Hooke's law state?
That the extension of the spring of the balance is proportional to the applied force as long as the elastic limit of the spring is not exceeded.
81
Does the spring balance have a uniform scale?
Yes.
82
What does the spring balance measure directly?
Weight.
83
How do you measure the weight of an object with a spring balance?
Suspend the object from the hook of the spring balance.
84
What does the weight cause the spring to do?
Stretch
85
How should the balance be held when taking a reading with a spring balance?
Still and vertically.
86
Where is it best to suspend a spring balance from?
A firm support or hook.
87
What should you do with the spring before taking readings?
Stretch it lightly with your hand and release it.
88
Why should you stretch and release the spring before taking readings?
To remove possible kinks in the spring.
89
Where should your eye be placed when taking a reading on a spring balance?
Horizontally with the pointer.
90
Why should your eye be placed horizontally with the pointer?
To avoid the error due to parallax.
91
How is time defined?
As that in which events are distinguishable with reference to before and after.
92
What is the most natural time unit?
The solar day.
93
What causes the solar day?
The passing of day and night.
94
How long does it take the earth to complete one revolution about its axis?
One solar day.
95
What time scale is used for astronomical purposes?
Sidereal time.
96
What is sidereal time?
The time interval between two successive passages of a star over the meridian.
97
What are the essential mechanisms of devices used for marking the passage of time?
Masses so mounted or suspended that when set in motion under the influence of forces
98
Give examples of such mechanisms.
The pendulum of a clock and the balance wheel of a watch.
99
What instruments are used to measure time in the laboratory?
A stop-clock or stop-watch.
100
How is a stop-clock or stop-watch started or stopped?
With the use of a knob.
101
How accurately can stop-watches measure time?
To 0.1 second.
102
What is the unit of time?
The second (s).
103
Give multiple units of the second.
60 seconds = 1 minute
104
What are the most accurate clocks?
Quartz crystal clock and the atomic clock.
105
What is said to have the dimension of length (L)?
Any quantity which can be measured in units of length.
106
What is said to have a dimension of Time (T)?
Any quantity which can be measured in units of time.
107
What is said to have a dimension of Mass (M)?
Any quantity which can be measured in units of mass.
108
What does the word "dimension" usually denote in Physics?
The physical nature of a quantity.
109
What symbols are used to specify length
mass
110
How are the dimensions of velocity (V) written?
V = [L] / [T] or [L][T⁻¹].
111
What is the dimension of area (A)?
[L] x [L] = [L²].
112
What is the dimension of volume (V)?
[L] x [L] x [L] = [L³].
113
What is the dimension of force?
[M] x [LT⁻²] = [MLT⁻²].
114
What is the dimension of pressure?
[MLT⁻²] / [L²] = [M L⁻¹ T⁻²].
115
What is the dimension of work?
[MLT⁻²] x [L] = [ML²T⁻²].
116
What is the use of dimensional analysis?
To verify whether a physical equation is correct or not.
117
What are derived quantities?
Quantities that are obtained by combination of fundamental quantities.
118
What are derived units?
The units of derived quantities.
119
Give examples of derived quantities and their units.
Area (m²)
120
How is the unit of area derived?
It is a product of length and breadth (m x m = m²).
121
How is the unit of volume derived?
It is a product of length
122
Why do units used in industry and business sometimes differ from those used in the laboratory?
Because in these areas
123
Give an example of a unit used for power in industry.
Horsepower (hp).
124
How much is one horsepower equal to?
0.746 kilowatts.
125
What unit is used to measure oil in oil industries?
Barrel.
126
Approximately how many liters are in a barrel of oil?
Between 120 and 159 liters.
127
What unit is used for measuring the area of land?
Hectare (ha).
128
How many square meters are in a hectare?
10
129
Are measurements in physics perfectly precise?
No.
130
What should you note about a measuring instrument when taking measurements?
The reading accuracy.
131
How should measurements be specified?
In the correct number of significant figures.
132
What is good practice when giving the result of a measurement?
To state the precision or estimated uncertainty.
133
What does the notation "51.3 ± 0.1 cm" mean?
That the length is probably between 51.2 and 51.4 cm.
134
What are significant figures?
The reliably known digits in a number.
135
How are significant figures usually determined?
As all figures from the first non-zero digit to the last non-zero digit
136
How many significant figures are in 51.35?
Four.
137
How many significant figures are in 0.053 cm?
Two.
138
What instruments are used to measure length in a secondary school physics laboratory?
Metre rule
139
What are the graduations on a metre rule?
Centimeters and millimeters.
140
What is the smallest graduation of a metre rule?
1 mm or 0.1 cm.
141
What is the reading accuracy of a metre rule?
0.1 cm.
142
What is the estimated uncertainty when measuring with a metre rule?
0.05 cm.
143
How can a length measurement with a metre rule be recorded?
As 21.55 ± 0.05 cm.
144
What precaution is necessary when measuring with a metre rule?
To avoid parallax error by looking vertically downwards on the markings.
145
What are steel tapes graduated in metres used for?
Measuring large distances like the length or width of a football field.
146
What is the purpose of vernier calipers?
To measure lengths more accurately than a metre rule.
147
What is the accuracy of vernier calipers?
To the nearest 0.1 mm.
148
Give examples of what vernier calipers can measure.
Thickness of a metre rule
149
What are the two scales on a vernier caliper?
The main scale and the vernier scale.
150
What does the vernier scale do?
It slides on the main scale and measures a fraction of the smallest division on the main scale.
151
What are the graduations on the main scale of a vernier caliper?
Centimeters and millimeters.
152
How is the vernier scale constructed?
By dividing a 9 mm length into 10 equal intervals.
153
What is the length of each vernier division?
0.9 mm or 0.09 cm.
154
What is the difference in length between a vernier scale division and a main scale division?
0.1 mm or 0.01 cm.
155
How is the total reading of a length obtained using a vernier caliper?
By adding the readings on both the main and vernier scales.
156
How do you record the reading on the main scale?
By noting the reading immediately preceding the zero mark on the vernier scale.
157
How do you record the reading on the vernier scale?
By noting the graduation on the vernier scale that aligns most directly with a graduation on the main scale.
158
What does the vernier scale reading give you?
The decimal place in millimeters or the second decimal place in centimeters.
159
What is the accuracy of vernier calipers?
0.01 cm.
160
What precaution should be taken when using a vernier caliper?
Always note if it has any zero error.
161
How do you check for zero error in a vernier caliper?
By setting the zeros of the main scale and the vernier scale to coincide.
162
What do you do if the zeros of the main scale and vernier scale do not coincide?
Note the difference as the 'zero error'.
163
How do you correct for zero error in subsequent readings?
Add or subtract the zero error as appropriate.
164
For what type of measurements is a micrometer screw gauge used?
Accurate measurements of small lengths.
165
Give examples of measurements taken with a micrometer screw gauge.
Diameter of a wire
166
What is the accuracy of a micrometer screw gauge?
0.001 cm.
167
What should be done before making measurements with a screw gauge?
Check for zero error.
168
What are the two scales on a micrometer screw gauge?
A main scale and a vernier scale.
169
What are the graduations on the main scale of a micrometer screw gauge?
Millimeters.
170
How many equal divisions are on the circular vernier scale of a micrometer screw gauge?
50
171
How far does the screw head move along the main scale when turned once?
0.5 mm.
172
What is the value of one division on the vernier scale of a micrometer screw gauge?
0.01 mm.
173
How can you obtain the volume of a rectangular block?
By measuring its length (l)
174
How can you obtain the volume of an irregular solid?
By immersing it completely in a measuring cylinder containing a liquid in which the solid is insoluble. The volume of the liquid displaced gives the volume of the solid.
175
How do you measure the volume of a sphere?
By measuring its diameter (d) with a micrometer screw gauge and using the formula V = (4/3)πr³
176
How do you measure the volume of a cylindrical wire?
By measuring the length (l) with a metre rule and the diameter (d) with a micrometer screw gauge and using the formula Volume = πr²l or π(d²/4)l.
177
What instruments can be used to measure the volume of a liquid?
A measuring cylinder
178
Where is the correct liquid level read in a graduated glass container?
At the bottom of the meniscus (or curved surface of the liquid).
179
How is mass defined?
As the quantity of matter or 'stuff' contained in a body.
180
How is weight defined?
As the force or pull with which the earth attracts the body towards the centre of the earth.
181
What instrument is used to measure mass?
A balance.
182
Name types of balances.
Beam or chemical balance
183
How is the mass of a body usually measured?
By comparing it with 'standard' masses.
184
How do you measure with a beam balance?
Place the object on the left-hand scale pan and standard masses on the right-hand scale pan.
185
What should the beam of the balance do when raised for weighing?
Swing freely about a pivot in the centre of the beam.
186
How do you know when the masses in the two scale pans are equal?
When the pointer swings equal number of divisions on each side of the central mark or the pointer balances on the central mark of the scale.
187
How do you obtain the mass of the object?
By adding the standard masses on the right scale pan.
188
On what principle does the beam balance work?
The principle of moments.
189
What is the reading accuracy of a beam balance?
Up to 0.001 grams.
190
What should you use for picking up standard masses when using a beam balance?
Forceps.
191
What should you do to objects before placing them on the scale pan?
Wipe them dry.
192
What should you do with hot objects before weighing them?
Allow them to cool.
193
When should you avoid adding or removing known masses from the scale pan?
While the beam is in the raised position.
194
What instrument is used to find the weight of an object?
A spring balance.
195
What law is the spring balance calibrated using?
Hooke's law.
196
What does Hooke's law state?
That the extension of the spring of the balance is proportional to the applied force as long as the elastic limit of the spring is not exceeded.
197
Does the spring balance have a uniform scale?
Yes.
198
What does the spring balance measure directly?
Weight.
199
How do you measure the weight of an object with a spring balance?
Suspend the object from the hook of the spring balance.
200
What does the weight cause the spring to do?
Stretch
201
How should the balance be held when taking a reading with a spring balance?
Still and vertically.
202
Where is it best to suspend a spring balance from?
A firm support or hook.
203
What should you do with the spring before taking readings?
Stretch it lightly with your hand and release it.
204
Why should you stretch and release the spring before taking readings?
To remove possible kinks in the spring.
205
Where should your eye be placed when taking a reading on a spring balance?
Horizontally with the pointer.
206
Why should your eye be placed horizontally with the pointer?
To avoid the error due to parallax.
207
How is time defined?
As that in which events are distinguishable with reference to before and after.
208
What is the most natural time unit?
The solar day.
209
What causes the solar day?
The passing of day and night.
210
How long does it take the earth to complete one revolution about its axis?
One solar day.
211
What time scale is used for astronomical purposes?
Sidereal time.
212
What is sidereal time?
The time interval between two successive passages of a star over the meridian.
213
What are the essential mechanisms of devices used for marking the passage of time?
Masses so mounted or suspended that when set in motion under the influence of forces
214
Give examples of such mechanisms.
The pendulum of a clock and the balance wheel of a watch.
215
What instruments are used to measure time in the laboratory?
A stop-clock or stop-watch.
216
How is a stop-clock or stop-watch started or stopped?
With the use of a knob.
217
How accurately can stop-watches measure time?
To 0.1 second.
218
What is the unit of time?
The second (s).
219
Give multiple units of the second.
60 seconds = 1 minute
220
What are the most accurate clocks?
Quartz crystal clock and the atomic clock.
221
What is said to have the dimension of length (L)?
Any quantity which can be measured in units of length.
222
What is said to have a dimension of Time (T)?
Any quantity which can be measured in units of time.
223
What is said to have a dimension of Mass (M)?
Any quantity which can be measured in units of mass.
224
What does the word "dimension" usually denote in Physics?
The physical nature of a quantity.
225
What symbols are used to specify length
mass
226
How are the dimensions of velocity (V) written?
V = [L] / [T] or [L][T⁻¹].
227
What is the dimension of area (A)?
[L] x [L] = [L²].
228
What is the dimension of volume (V)?
[L] x [L] x [L] = [L³].
229
What is the dimension of force?
[M] x [LT⁻²] = [MLT⁻²].
230
What is the dimension of pressure?
[MLT⁻²] / [L²] = [M L⁻¹ T⁻²].
231
What is the dimension of work?
[MLT⁻²] x [L] = [ML²T⁻²].
232
What is the use of dimensional analysis?
To verify whether a physical equation is correct or not.
