- (a) mm < cm < m < km
- (b) mm > cm > m > km
- (c) km < m < cm < mm
- (d) mm > m > cm > km
Answer:
(a) mm < cm < m < km
- (a) mass
- (b) weight
- (c) time
- (d) length
Answer:
(d) length
- (a) 100 quintals
- (b) 10 quintals
- (c) 1/10 quintals
- (d) 1/100 quintals
Answer:
(b) 10 quintals
- (a) Spring balance
- (b) Beam balance
- (c) Physical balance
- (d) Digital balance
Answer:
(a) Spring balance
- Metre is the unit of length.
- 1 kg of rice is weighed by beam balance.
- Thickness of a cricket ball is measured by vernier caliper.
- Radius of a thin wire is measured by screw gauge.
- A physical balance measures small differences in mass up to 1 mg or less.
If false, correct the statement.
Answer: False. The statement is incorrect. The SI unit of electric current is ampere (A), not kilogram. Kilogram is the SI unit of mass. Electric current measures the flow of electric charge through a conductor, and it is measured in amperes using an ammeter. This is one of the seven fundamental SI units in the International System of Units.
Answer: True. Kilometre is indeed one of the SI units of measurement for length and distance. It is derived from the metre, which is the fundamental SI unit of length. One kilometre equals 1000 metres. The kilometre is widely used in everyday life and in scientific measurements, particularly for measuring large distances such as the distance between cities or geographical features.
Answer: True. In everyday life, we commonly use the term weight instead of mass, even though they are scientifically different. Weight is the force exerted by gravity on an object and varies with location, while mass is the amount of matter in an object and remains constant. However, in casual conversation, people often use weight and mass interchangeably when referring to how heavy something is, which is why this statement is true in the context of everyday usage.
Answer: True. A physical balance is more sensitive than a beam balance. A physical balance can detect smaller differences in mass and provides greater precision in measurements. This is because a physical balance has a more delicate construction and can measure mass to a higher degree of accuracy compared to a beam balance, which is a simpler instrument. The physical balance is therefore preferred in laboratories when precise measurements are required.
Answer: True. One Celsius degree is an interval of 1 K (kelvin), meaning that a temperature change of one degree on the Celsius scale is equivalent to a change of one kelvin on the absolute temperature scale. Additionally, zero degree Celsius is equal to 273.15 K. This relationship shows that the Celsius and Kelvin scales have the same interval size, but differ in their reference points. The Kelvin scale is the absolute temperature scale used in the SI system.
Answer: True. With the help of a vernier caliper, we can achieve an accuracy of 0.1 mm, while with a screw gauge we can achieve an accuracy of 0.01 mm. This means that a screw gauge is ten times more precise than a vernier caliper. The screw gauge is used for measuring very small lengths and diameters with high precision, whereas the vernier caliper is used for measuring lengths, diameters, and depths with moderate precision. Both instruments are essential measuring tools in physics laboratories.
| Quantity | Unit |
|---|---|
| Length | metre |
| Mass | kilogram |
| Time | second |
| Temperature | kelvin |
| Instrument | Used For |
|---|---|
| Screw gauge | Coins |
| Vernier caliper | Cricket ball |
| Beam balance | Vegetables |
| Digital balance | Gold ornaments |
Choose the correct answer:
- (a) Both A and R are true but R is not the correct reason.
- (b) Both A and R are true and R is the correct reason.
- (c) A is true but R is false.
- (d) A is false but R is true.
Assertion (A):
The scientifically correct expression is “The mass of the bag is 10 kg”.
Reason (R):
In everyday life, we use the term weight instead of mass.
Answer:
(a) Both A and R are true but R is not the correct reason.
Assertion (A):
0°C = 273.15 K. For convenience, it is rounded off to 273 K.
Reason (R):
To convert Celsius temperature into Kelvin, we add 273 to the given temperature.
Answer:
(b) Both A and R are true and R is the correct reason.
Answer: (b) Both A and R are true and R is the correct reason. The assertion that distance between two celestial bodies is measured in terms of light year is true. The reason that the distance travelled by light in one year is one light year is also true and correctly explains why light years are used for astronomical measurements. A light year is a unit of distance, not time, and represents the vast distances between stars and galaxies. Since ordinary units like metres or kilometres are impractically large for cosmic distances, astronomers use light years to express these enormous distances in more manageable numbers.
Answer: Measurement is the process of comparing a given physical quantity with a known standard quantity of the same nature. In other words, measurement involves determining how many times a standard unit is contained in the physical quantity being measured. For example, when we measure the length of a table, we compare it with a standard unit of length such as a metre. Measurement is fundamental to science and allows us to quantify physical properties in a way that can be communicated and verified by others.
Answer: A standard unit is a fixed quantity of constant magnitude that is used as a reference to measure other quantities of the same nature. Standard units are internationally agreed upon and remain unchanged, ensuring consistency and uniformity in measurements across different regions and countries. For example, the metre is the standard unit of length, the kilogram is the standard unit of mass, and the second is the standard unit of time. These standard units form the basis of the SI system and allow scientists and people worldwide to communicate measurements accurately.
Answer: The full form of SI system is International System of Units. This is the modern metric system of measurement that is used worldwide in science, technology, and commerce. The SI system was established to provide a uniform and standardized set of units for all physical quantities. It consists of seven fundamental units: metre for length, kilogram for mass, second for time, ampere for electric current, kelvin for temperature, mole for amount of substance, and candela for luminous intensity.
Answer:
The least count of an instrument is the smallest measurement that can be measured accurately using that instrument.
Formulae:
For Vernier Caliper:
For Screw Gauge:
Answer:
Pitch of a screw gauge is the distance moved by the screw in one complete rotation.
Answer:
No. A ruler is not accurate enough to measure the diameter of a thin wire. A screw gauge is used instead.
Answer:
- Units named after scientists are written in lowercase letters.
Example: joule, kelvin, newton
- Symbols are generally written in lowercase.
Example: m, kg, s
- Symbols derived from scientists’ names are written in capital letters.
Example: N, J, C
- Symbols are not followed by a full stop.
Example: 75 cm
- Symbols are never written in plural form.
Example: 100 kg (not 100 kgs)
Answer: Standard units are needed to maintain uniformity and accuracy in measurements throughout the world. Without standard units, different regions and countries would use different units for the same physical quantity, making it impossible to compare measurements or communicate scientific findings accurately. Standard units ensure that a measurement made in one part of the world can be understood and verified in another part. They also allow scientists to conduct experiments and share results with confidence, knowing that everyone is using the same reference standards. This universal agreement on standard units is essential for scientific progress and international cooperation.
| Mass | Weight |
|---|---|
| Fundamental quantity | Derived quantity |
| Scalar quantity | Vector quantity |
| Amount of matter in a body | Gravitational force acting on a body |
| Constant everywhere | Varies from place to place |
| Measured using physical balance | Measured using spring balance |
| SI unit: kilogram (kg) | SI unit: newton (N) |
Answer:
It is the minimum value measured accurately using a vernier caliper.
Answer:
Procedure:
- Determine the pitch and least count of the screw gauge.
- Place the tea cup between the studs.
- Rotate the ratchet until the cup is held gently.
- Note the pitch scale reading (PSR).
- Note the head scale coincidence (HSC).
- Calculate thickness using:
- Repeat readings at different positions and calculate the average.
Answer:
Procedure:
- Determine the pitch and least count of the screw gauge.
- Place the coin between the studs.
- Rotate the ratchet gently.
- Note PSR and HSC.
- Calculate thickness using:
- Repeat readings and calculate the average value.
Question:
Inian says one light year is (9.46 \times 10^{15}) m.
Ezhilan says it is (9.46 \times 10^{12}) km.
Who is correct?
Solution:
Both are correct because:
Given:
- MSR = 7 cm
- VC = 6
- LC = 0.01 cm
Diameter:
Radius:
Correction made:
Original answer incorrectly converted units to metres.
Given:
- PSR = 1 mm
- HSC = 68
- LC = 0.01 mm
Calculation:
Given:
Using:
Using Vernier Caliper to Find the Outer Diameter of a Pen Cap
Aim:
To find the outer diameter of a pen cap.
Materials Required:
- Vernier caliper
- Pen cap
Result:
The outer diameter of the pen cap = 9.35 cm
Possible textbook typo noted:
A pen cap diameter is usually around 0.935 cm or 9.35 mm.
Determining Thickness of a Single Sheet Using Screw Gauge
Result:
The thickness of a single sheet = 0.30 mm
Given:
Using:
Given:
40 apples = 5 kg = 5000 g
(i) Mass of 12 apples
(ii) Mass of one apple
Answer:
Mass of one apple = 125 g
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