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Physics Keypoints; MEASUREMENTS AND UNITS; Physics deals with the study of matter and energy, and measurements and units play a vital role in this subject. Accurate measurements of physical quantities are crucial for scientific investigations and technological advancements. In this class, we will discuss various measurements and units used in physics.

Check our physics past questions

(a) Length, Area, and Volume: Length, area, and volume are basic physical quantities that we measure. The most common measuring instruments for these quantities are:

  • Meter Rule: A long straight edge, calibrated in centimeters and millimeters, is used to measure lengths.
  • Vernier Calipers: An instrument that measures objects’ internal and external dimensions with high accuracy. It has two scales, one of which is fixed and the other is movable.
  • Micrometer Screw-gauge: A device used to measure the thickness of objects, with a high degree of accuracy.
  • Measuring Cylinder: A glass or plastic container, calibrated in milliliters, used to measure the volume of liquids.

(b) Mass:

Mass is a fundamental physical quantity that we measure. The most common instrument used for measuring mass is a simple beam balance. A beam balance consists of a lever with two pans hanging from each end. The object whose mass is to be measured is placed on one pan, and standard weights are placed on the other until the beam balances. The concept of beam balance is based on the principle of moments.

(c) Time:

Time is another fundamental physical quantity that we measure. The most common unit of time is the second. Time can be measured using various devices, such as a stopwatch, clock, or sundial.

(d) Fundamental Physical Quantities:

There are seven fundamental physical quantities:

  • Length
  • Mass
  • Time
  • Electric Current
  • Temperature
  • Amount of substance
  • Luminous intensity

(e) Derived Physical Quantities and their Units:

Derived physical quantities are obtained by combining fundamental physical quantities. For example, speed is obtained by dividing distance by time. The units of derived physical quantities are obtained by combining the units of fundamental physical quantities. For example, the unit of speed is meters per second (m/s).

(f) Dimensions:

Dimensions are the powers to which fundamental quantities are raised in a physical quantity. The dimensions of a physical quantity are expressed using square brackets. For example, the dimensions of speed are [L][T]^-1, where L is the dimension of length and T is the dimension of time.

(g) Limitations of Experimental Measurements:

Experimental measurements have limitations due to the following reasons:

  • Accuracy of Measuring Instruments: The accuracy of a measuring instrument is the degree of closeness of its readings to the true value. The accuracy of a measuring instrument depends on its design, construction, and calibration.
  • Simple Estimation of Errors: Errors can occur due to various reasons, such as the limitations of the measuring instrument, human error, and environmental factors. A simple estimation of errors can be obtained by taking repeated measurements and calculating the mean and standard deviation.
  • Significant Figures: Significant figures are the meaningful digits in a measured quantity. The number of significant figures depends on the precision of the measuring instrument.
  • Standard Form: Standard form is a way of expressing very large or very small numbers in a compact form using powers of 10.

(h) Measurement, Position, Distance, and Displacement:

Measurement is the process of determining the value of a physical quantity. The position is the location of an object in space, and it is defined using coordinates. Distance is the length of the path traveled by an object, while displacement is the change in the position of an object. Displacement is a vector quantity that has both magnitude and direction. The frame of reference is the coordinate system used to define the position of an object.

Formulas; Physics Keypoints; MEASUREMENTS AND UNITS

  1. Formula for speed: Speed = Distance / Time
  2. Formula for acceleration: Acceleration = Change in Velocity / Time
  3. Formula for force: Force = Mass x Acceleration
  4. Formula for work: Work = Force x Distance
  5. Formula for power: Power = Work / Time
  6. Formula for density: Density = Mass / Volume
  7. Formula for pressure: Pressure = Force / Area
  8. Formula for simple harmonic motion: Period = 2 x π x √(m/k)

Where m is the mass of the object and k is the spring constant.

These formulas are some of the most basic and commonly used in physics and can be useful for solving problems and understanding the concepts covered in this topic.

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