10 Questions
What is the formula to express the area of a rectangle?
Area = length × breadth or Area = length × length
What is the SI unit of area?
m2 or squared metre
What is the formula to express force in terms of mass and acceleration?
Force = mass × acceleration
What is the SI unit of force?
kg m/s2 or kg ms–2
What is the relationship between acceleration and change in velocity?
Acceleration is equal to change in velocity per unit time
How is the derived unit for area obtained?
By substituting the units of the base physical quantities, metre, in the formula for area
What is the meaning of m2 as the SI unit of area?
m2 is pronounced as squared metre
How is the formula for force related to the base physical quantities?
Force is related to mass, length, and time through the formula Force = mass × (length/time) × (1/time)
What are the base physical quantities involved in the formula for force?
Mass, length, and time
What is the significance of Table 1.2 in the context of physical quantities?
It provides the relationship between some commonly encountered physical quantities and their SI units
Study Notes
Objectives of Measurement
- Define measurement and explain the need for measurement
- Give examples of body parts used to measure length of an object and state limitations
- Describe ancient measurement systems, including Indian and others
- Explain the need for a common system of units
- Define and differentiate base and derived SI units
- Derive the SI unit of a physical quantity
- Explain the need of SI prefixes
- Use SI prefixes correctly for units and write SI units using the rules
What is Measurement?
- Measurement is a counting of the number of times a chosen scale is used
- It involves comparing the object to be measured with a standard unit
- Lord Kelvin: "When you can measure what you are talking about, and express in numbers, you know what you are talking about"
Why Measure?
- Measurement is essential in everyday life
- Accurate measurement is desirable for both buyer and seller
- Absence of suitable measurement can lead to conflicts
- Measurement is crucial in space science, medicine, and other fields
Indian Measurement System
- In ancient India, lengths of shadows were used to know the approximate time of day
- Long time durations were expressed in terms of lunar cycles
- In Mohenjodaro era, size of bricks was standardized with length, breadth, and width in the ratio of 4:2:1
- During Chandragupta Maurya period, there was a well-defined system of weights and measures
Derived Units
- Derived units are physical quantities that can be derived in terms of base units
- Examples of derived units: area (m2), volume (m3), force (kg m/s2)
- To derive a unit, find the relationship between the physical quantity and base physical quantities, then substitute the units of the base physical quantities
Learn about the importance of measurement, different measurement systems used in ancient times, and the need for a common system of units. Understand base and derived SI units and their applications.
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