Key Point: Introduction To Physics, Physical Quantities, Base Quantities, Derived Quantities, International System of Units, Base Units, Derived Units.
1.2 What is the difference between base quantities and de quantities? Give three examples in each case.
... Answer:
Difference between base quantities and derived quantities:
Base quantities:
Base quantities are the quantities on the basis of which other quantities expressed. There are seven physical quantities which form the foundation for other physical quantities. These physical quantities are called the base quantities.
Examples:
Length, mass, time, electric current, temperature, intensity of light and the amount of a substance.
Derived quantities:
The quantities that are expressed in terms of base quantities are called derived quantities.
Examples:
Area, volume, speed, force, work, energy, power, electric charge, electric potential, etc.
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1.3. Pick out the base units in the following: joule, newton, kilogramme, hertz, mole, ampere, metre, kelvin, coulomb and watt.
... Answer:
Base units:
kilogramme, mole, ampere, metre, Kelvin.
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1.4. Find the base quantities involved in each of the following derived quantities: (a) speed (b) volume (c) force (d) work
... Answer:(a) speed
Speed = distance covered / time taken = m / s
Base quantities involved in speed are length and time.
(b) Volume:
Volume = length x width x height = m³
Base quantity involved in volume is length.
(c) Force:
Force F = ma IN = 1 kg x 1 m s⁻² IN = kg m s⁻²
Base quantities involved in force are mass, length, and time.
(d) Work:
Work done = Force x displacement
W = F S = 1 J = 1N x 1 m =1 kg m s⁻² x 1 m = 1 kg m²s ⁻²
Base quantities involved in work are mass, length, and time.
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1.5. Estimate your age in seconds.
... Answer:
We know that
:: 1 year = 365 days
:: 1 day = 24 Hours
:: 1 hour = 60 Minutes
:: 1 minute = 60 second
Suppose my age = 15 years
= 15 x 365 = 5475 days
= 5475 x 24 = 131400 hours
= 131400 x 60 = 7884000 minutes
= 7884000 x 60 = 473040000 seconds
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1.6. What role Sl units have played in the development of science?
... Answer:
i. SI system is in use all over the world.
ii. Manipulation in this system is quite easy i.e. the multiple and sub multiple of different units are obtain simply by multiplying or dividing with ten or powers of tens.
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1.7. What is meant by Vernier constant?
... Answer:
Vernier constant is called as Least count (LC): It is the difference between one small division on main scale division and one Vernier scale division ( 0.1 mm ). It is called least count (LC) of the Vernier Calipers. Least count of the Vernier Calipers can also be found as given below:
Least count of Vernier Calipers = smallest reading on main scale / number of divisions on Vernier scale
LC = 1 mm / 10 divisions
LC= 0.1 mm = 0.01 cm
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1.8. What do you understand by the zero error of a measuring instrument?
... Answer:
Zero Error and Zero Correction:
It is a defect in a measuring devices (Vernier Calipers & Screw Gauge) & zero error is caused by an incorrect position of the zero point.
For Example: To find the zero error, close the jaws of Vernier Calipers gently. If zero ne Vernier scale coincides with the zero of the main scale then the zero error is zero. Zero error will exist if zero line of the Vernier scale is not coinciding zero of main scale.
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1.9. Why is the use of zero error necessary in a measuring instrument?
... Answer:. Sand
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1.10. What is a stopwatch? What is the least count of a mechanical stopwatch you have used in the laboratories?
... Answer:. Experiments
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1.11. Why do we need to measure extremely small interval of times?
... Answer:. Anderson`
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1.12. What is meant by significant figures of a measurement? How is precision related to the significant figures in a measured quantity?
... Answer:. Archimedes
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1.13. What is meant by significant figures of a measurement? How is precision related to the significant figures in a measured quantity?
... Answer:. Archimedes
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1.3. Pick out the base units in the following: joule, newton, kilogramme, hertz, mole, ampere, metre, kelvin, coulomb and watt.
Base units:
kilogramme, mole, ampere, metre, Kelvin.
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1.4. Find the base quantities involved in each of the following derived quantities: (a) speed (b) volume (c) force (d) work
Speed = distance covered / time taken = m / s
Base quantities involved in speed are length and time.
(b) Volume:
Volume = length x width x height = m³
Base quantity involved in volume is length.
(c) Force:
Force F = ma IN = 1 kg x 1 m s⁻² IN = kg m s⁻²
Base quantities involved in force are mass, length, and time.
(d) Work:
Work done = Force x displacement
W = F S = 1 J = 1N x 1 m =1 kg m s⁻² x 1 m = 1 kg m²s ⁻²
Base quantities involved in work are mass, length, and time.
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1.5. Estimate your age in seconds.
We know that
:: 1 year = 365 days
:: 1 day = 24 Hours
:: 1 hour = 60 Minutes
:: 1 minute = 60 second
Suppose my age = 15 years
= 15 x 365 = 5475 days
= 5475 x 24 = 131400 hours
= 131400 x 60 = 7884000 minutes
= 7884000 x 60 = 473040000 seconds
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1.6. What role Sl units have played in the development of science?
i. SI system is in use all over the world.
ii. Manipulation in this system is quite easy i.e. the multiple and sub multiple of different units are obtain simply by multiplying or dividing with ten or powers of tens.
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1.7. What is meant by Vernier constant?
Vernier constant is called as Least count (LC): It is the difference between one small division on main scale division and one Vernier scale division ( 0.1 mm ). It is called least count (LC) of the Vernier Calipers. Least count of the Vernier Calipers can also be found as given below:
Least count of Vernier Calipers = smallest reading on main scale / number of divisions on Vernier scale
LC = 1 mm / 10 divisions
LC= 0.1 mm = 0.01 cm
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1.8. What do you understand by the zero error of a measuring instrument?
Zero Error and Zero Correction:
It is a defect in a measuring devices (Vernier Calipers & Screw Gauge) & zero error is caused by an incorrect position of the zero point.
For Example: To find the zero error, close the jaws of Vernier Calipers gently. If zero ne Vernier scale coincides with the zero of the main scale then the zero error is zero. Zero error will exist if zero line of the Vernier scale is not coinciding zero of main scale.
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1.9. Why is the use of zero error necessary in a measuring instrument?
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1.10. What is a stopwatch? What is the least count of a mechanical stopwatch you have used in the laboratories?
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1.11. Why do we need to measure extremely small interval of times?
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1.12. What is meant by significant figures of a measurement? How is precision related to the significant figures in a measured quantity?
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1.13. What is meant by significant figures of a measurement? How is precision related to the significant figures in a measured quantity?
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