Physical Quantities
and
Measurement
EXERCISES
BE PROMPT
A. Fill in the blanks.
1. The quantities which are unique and do not depend on other quantities are called fundamental quantities.
2. Decametre is 1/10 of metre.
3. 1000 kg is equal to 1 tonne.
4. Area of an object can be determined using graph paper.
5. Stop clock is used to measure smaller time intervals.
6. Thermometer is used to measure the temperature of an object.
B. State whether the following statements are true (T) or false (F). Correct the false statements.
1. Hectare is the unit of time. [F]
= Hectare is the unit of area.
2. 1 solar day is equal to 86,000 second. [F]
= 1 solar day is equal to 86,400 second.
3. Parallax error is the error in measurement of length due to a faulty instrument. [F]
= Parallax error is the error in measurement of length due to wrong position of the eye.
4. 1 decimetre is equal to 10 metre. [F]
= 1 decimetre is equal to 1/10 metre.
5. The two pans of a beam balance are suspended such that they are equidistant from the centre of the beam. [T]
6. The normal temperature of a normal human body is 42℃. [F]
= The normal temperature of a normal human body is 37℃.
C. Choose the correct option.
1. Which of the following is not a fundamental quantity?
a) Current. [ ]
b) Time. [ ]
c) Weight. [✓]
d) Length. [ ]
2. A physical balance is used for the measurement of _________ .
a) length. [ ]
b) volume. [ ]
c) area. [ ]
d) mass. [✓]
3. 1 micron is equal to ______ metres.
a) 10-2 [ ]
b) 10 [ ]
c) 10-6 [✓]
d) 106 [ ]
4. Vernier calliper is used to measure ________ .
a) mass. [ ]
b) length. [✓]
c) area. [ ]
d) none of these. [ ]
5. Doctor's thermometer is another name for ________ .
a) clinical thermometer. [✓]
b) laboratory thermometer. [ ]
c) maximum-minimum thermometer. [ ]
d) none of these. [ ]
6. A kink is present in _________ .
a) clinical thermometer. [✓]
b) laboratory thermometer. [ ]
c) both (a) and (b). [ ]
d) none of these. [ ]
D. Match the columns.
=
|
Column
A |
Column
B |
|---|---|
|
1. Length |
a)
Pendulum. [4] |
|
2.
-10℃ to 110℃ |
b)
Tonne. [3] |
|
3. Mass |
c) Clinical Thermometer. [5] |
|
4. Time |
d) Laboratory thermometer. [2] |
|
5. measuring human body temperature |
e) Screw gauge. [1] |
SHORT AND PRECISE
A. Show the given text in form of the flowchart.
1. Fundamental quantities and derived quantities.
=
2. Measuring mass, length, time and temperature, and the instruments used for measuring these quantities.
=
B. Give reasons for the following statements.
1. The system of units should be uniform everywhere to avoid confusion in measurement.
= The system of units should be uniform everywhere to avoid confusion as the non-standard units like - footstep, handspan and cubits etc. could not be taken as reliable because they vary person to person.
2. A tailor uses measuring tape for taking measurements.
= A tailor uses measuring tape for taking measurements because it is a flexible ruler made of a ribbon of cloth, plastic or metal strip. It can be easily carried in pocket and can be used to measure around curves or corners of objects. We have many curves in our body. So this is helpful for tailors to measure our body to sew clothes.
3. While taking reading from a ruler, the eye must be exactly vertically above the mark to be read.
= While taking reading from a ruler, the eye must be exactly vertically above the mark to be read because in other positions of the eye, the reading is either more or less than the actual reading.
4. Electronic weighing machines are used in laboratories.
= Electronic weighing machines are used in laboratories due to their high degree of accuracy in measuring mass of different objects, especially small objects.
5. There are multiples and sub-multiples of various units.
= There are multiples and sub-multiples of various units to deal with different magnitudes of physical quantities. To create larger forms of units, multiples of units are used. Submultiples of units are used to get smaller forms of units.
6. A thermometer should be given jerks before using it again.
= A thermometer should be given jerks to bring back the mercury to the bulb before using it again.
C. Answer in short.
1. Give an example where exact measurement is necessary.
= In the scientific laboratories, exact measurement is necessary for scientific purposes.
2. Give two examples of physical quantities.
= Two examples of physical quantities are - length and mass.
3. Define parallax error.
= Parallax error is an error in measurement that arises due to wrong positioning of the eye.
4. What are the two important things to be mentioned when specifying measurement of a physical quantity?
= The two important things to be mentioned when specifying measurement of a physical quantity are -
❐ The unit of measurement.
❐ The magnitude of measurement, i.e., a value that represents the number of units contained in that quantity.
5. Name any two multiples and sub-multiples of metre and show their relationship.
= Two multiples of metre are - Kilometre and Hectometre.
1 kilometre = 1000 metre
1 hectometre = 100 metre
Two submultiples of metre are - Centimetre and Millimetre.
1 Centimetre = 0.01 metre
1 Millimetre = 0.001 metre
6. Give the formulae for calculating the area of the following figures.
a) Square;
b) Triangle;
c) Circle;
d) Rectangle;
= The formula of calculating the area of -
a) Square = Side ✕ Side
b) Triangle = (1/2) ✕ Base ✕ Height
c) Circle = 𐍀 ✕ (Radius)²
d) Rectangle = Length ✕ Breadth
7. Why do we use a measuring tape?
= A measuring tape is used to measure long lengths of straight or curved objects. It is flexible ruler made of a ribbon of clothe, plastic or metal strip. It can be easily carried in pocket and can be used to measure around curves or corners of objects.
8. Name two methods for calculating area of regular shapes.
= Two methods for calculating area of rectangular shapes are -
i) Using Standard Formulae : The area of rectangular surfaces such as square, rectangle and triangle is easy to calculate because there are specific formulae for each of them.
ii) Using Graph Paper : Area of regular surfaces or objects can also be measured by using graph paper.
9. Where do we commonly use a stop watch?
= We commonly use a stopwatch in time-bound activities like sporting events, debate competitions, extempore and many others.
10. What is the role of kink in a clinical thermometer?
= Actually when the thermometer is taken out of the mouth, the mercury in the bulb contracts as the temperature outside our body is normally less and the mercury column breaks at the kink. Thus, the level of mercury remains constant even after taking the thermometer out of the mouth.
AT LENGTH
A. Explain the following terms.
1. Measurement.
= Measurement is the comparison of an unknown quantity with a known fixed quantity.
2. Physical quantity.
= Physical quantity is a quantity that can be measured.
3. Derived quantity.
= Derived quantity is the quantities that are derived from fundamental quantities.
4. Mass.
= Mass is the amount of matter contained in an object.
5. Temperature.
= Temperature is the measure of degree of hotness or coldness.
6. Time.
= Time is the interval between two events.
B. Differentiate between the following.
1. Fundamental quantities and derived quantities.
=
|
Fundamental Quantities |
Derived Quantities |
|---|---|
|
1. Fundamental quantities are those physical quantities that are
unique and do not depend on any other quantity. |
1. Derived quantities are those quantities that are derived from
fundamental quantities. |
|
2. For Example – Length, mass, time etc. |
2. For Example – Volume, speed, force etc. |
2. Beam balance and electronic balance.
=
|
Beam Balance |
Electronic Balance |
|---|---|
|
1. It has two pans to hold object and weights. |
1. It has only once pan to hold the object. |
|
2. It does not provide accurate measurement. |
2. It provides absolutely accurate measurement. |
|
3. It does not need electric power to run. |
3. It needs electric power to run. |
3. Clinical thermometer and laboratory thermometer.
=
|
Clinical Thermometer |
Laboratory Thermometer |
|---|---|
|
1. It shows temperature from 35℃ to 42 |
|
|
|
|
C. Read the given process to measure area of a regular object using graph paper carefully. Identify the incorrect parts of the process.
❐ Place the object on a graph paper and mark a line far away from its outline with a marker.
❐ You will observe that the outline of the object encloses on the graph paper.
❐ Mark the complete squares with a tick and the squares that are less than half-covered with a cross.
❐ Count the number of squares that are marked with ticks and crosses, and also count the squares that are less than half.
❐ Now divide the sum of all marked squares by the area of each square to get an approximate area of the object.
=
❐ Place the object on a graph paper and mark an outline of the object with a marker.
❐ You will observe that the outline of the object encloses on the graph paper.
❐ Mark the complete squares with a tick and the squares that are more than half-covered with a cross.
❐ Count the number of squares that are marked with ticks and crosses, and ignore the squares that are less than half.
❐ Now multiple the sum of all marked squares by the area of each square to get an approximate area of the object.
D. Answer in detail.
1. Write the steps to be followed while measuring a length using ruler.
= To measure the length of any material using the ruler, the steps given below should be followed :
❐ Place the ruler along the length to be measured, parallel to its graduation (the markings on a ruler).
❐ Make sure that the zero mark of the ruler coincides with one of the ends of the length to be measured.
❐ In some rulers, the ends may be broken and the zero mark may not be clearly visible. In such cases, some other digit say mark 1 can be taken as the initial reading. You must remember the digit taken and subtract it from the final reading at the other end to get an accurate measurement of length.
❐ For taking measurements, correct position of the eye is also very important. The eye must be exactly vertically above the mark to be read. In other positions of the eye, the reading is either more or less than the actual reading. Such an error in measurement that arises due to wrong position of the eye is called parallax error.
2. How can we calculate the area of a match-box?
= A match box has six surfaces alternate two of them are the same. If we consider that the length of the match box is L and the breadth is B and the height is H, then the area of one pair of surface of the match box will be (L✕B), the other will be (B✕H) and the last will be (L✕H).
As the three types of surfaces are in pairs, so the ultimate calculation is =
2(L✕B)+2(B✕H)+2(L✕H)
= 2LB+2BH+2LH
3. Write a note on a beam balance.
= A beam balance consists of a horizontal metallic beam with a support and a pointer at its centre. The beam can move freely about the support. From the ends of the beam, two similar pans are suspended such that they are equidistant from the centre of the beam.
Principle: When both the pans are empty or loaded with equal masses, a state of equilibrium (balance) is achieved. In such a state, the beam is horizontal and the pointer points vertically up.
Working: To find the mass of an object, it is placed on one pan and standard weights are kept on the other pan of the beam balance. The standard weights are available in different sizes and masses like 5g, 10g, 20g, 50g, 100g, and 500g to measure smaller masses and 1kg, 2kg, 10kg and 20kg to measure bigger masses. The weights are adjusted till the beam is horizontal and the pointer points vertically up. The sum of the masses of the standard weights gives the mass of the object.
4. How does a pendulum clock work?
= A pendulum clock works on the principle of a simple pendulum and uses a swinging pendulum as its time keeping element. The time taken by the pendulum to go from one extreme to the other is equal to 1 second, so it completes one to and fro motion in two seconds. The dial of the clock consists of twelve big markings (either number of bold marks) which represent the hours. These markings are further divided into 5 smaller divisions, giving a total of 60 small divisions.
These smaller divisions indicate the minutes. There are three needles namely hour arm, minute arm and second arm, attached from the centre of the dial with the help of gear wheels. As the pendulum of the clock moves from one end to the other, the second's arm moves ahead by one small division.
Once the second's arm completes 60 small divisions, i.e., it moves one full round of the circular dial, the minute's arm moves to the next small division. Once the minute hand also goes once round the dial covering 60 small divisions, the hour hand reaches the next big marking indicating that 1 hour has gone past.
5. How is a laboratory thermometer different from a clinical thermometer? Also, mention the precautions to be observed while using a laboratory thermometer.
= A laboratory thermometer shows of
The precautions to be observed while using a laboratory thermometer are -
❐ A laboratory thermometer should always be kept upright and not tilted.
❐ The bulb of the thermometer should be properly dipped in the substance whose temperature is to be measured.
❐ The bulb should not touch the base or the side of the container.
E. Make the following conversions.
1. 150 cm = 1.5 m = 15 dam;
2. 2 dam = 200 mm;
3. 3 ft = 36 inches;
4. 4.2 km = 4200 m;
5. 2 lb = 907.18 g;
6. 4 g = 4000 mg;
7. 2 quintal = 200 kg;
8. 3.5 hectare = 35000 m²;
9. 4 min = 240 s;
10. 5 h = 300 min;
11. 101.85 ℃ = 375 K;
12. 200 ℃ = 392 ℉ = 473 K;