Physics Class 11 Lecture Notes

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Physical Quantities and Measurements

Physical Quantities

• Definition: Quantities that can be measured.
• Examples: Time, Temperature, Length, Mass.

Non-Physical Quantities

• Definition: Quantities that cannot be measured.
• Examples: Emotions like anger, love.

Measurements

• Definition: The process of measuring something.

Experimental Observation

Types of Observations

1. Qualitative Observations

   • Deal with data observed by senses: sight, smell, taste, hearing.
   • Examples: Observing a chair, tasting food.
   • No measurements or numbers involved.

2. Quantitative Observations

   • Observations that can be measured.
   • Examples: Duration of a lecture, force applied.

Estimation of Physical Quantities

• Not accurate readings, but close to real values.
• Based on experience and physical reasoning.

Estimation Examples

1. Height of a Building

   • Count floors and estimate the height of each floor.
   • Multiply to get the building's height.

2. Thickness of Paper

   • Measure a stack of papers and divide by the number of pages.

Estimation of Mass from Volume and Density

• First estimate volume, then mass using density.
• Formula: Density = Mass / Volume

Units and Measurements

Base Quantities

• Fundamental physical quantities: Length, Mass, Time, Electric Current, Temperature, Amount of Substance, Intensity.

Derived Quantities and Units

• Quantities derived from base quantities.
• Examples of derived units and their base unit expressions:

Force (Newtons)

• Formula: F = m * a
• Units: kg * m / s²

Work (Joules)

• Formula: W = F * d
• Units: kg * m² / s²

Power (Watts)

• Formula: P = W / t
• Units: kg * m² / s³

Pressure (Pascals)

• Formula: P = F / A
• Units: kg / m * s²

Charge (Coulombs)

• Formula: Q = I * t
• Units: A * s

Suggestions and Feedback

• At the end, feedback is sought from you on how the lecture can be improved.

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