This document discusses different units and measurements of length, mass, time, and other topics. It covers measuring length using parallax methods and ranges from the size of atoms to astronomical units. Mass is measured using gravitational and mass spectrograph methods. Accuracy and precision, errors, and significant figures are also mentioned. The document provides examples of calculating distance to the moon using parallax and the diameter of the sun using its angular size and distance from Earth.

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Units and Measurements
Presented by
Sana

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Lets talk about
■ Measurment of length
■ Measurement of mass
■ Measurment of time
■ Accuracy and precision
■ Errors
■ Significant figures
■ Dimensions

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Measurment of length

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Parallax method
The effect whereby the position or direction of an object
appears to differ when viewed from different positions.

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Range of length
Atom
1 fermi = 10-15 m
1 Angstorm = 10-10m
Astronomical Unit (AU)
1 AU = distance between Sun &
Earth
1 AU = 1.496*10¹¹m
Light-year
It is the distance light travels in
one Earth year.
ly = 9.46*1015
m

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The moon is observed from two diametrically opposite points A and B on
Earth.The angle subtended at the moon by the two directions of observation
is 1° 54'.Given the diameter of the Earth to be about 1.276 * 10 ^ 7 m,
compute the distance of the moon from the Earth.
? The Sun's angular diameter is measured to be 1920’’.The distance of the sun
from the earth is 1.496 ×10^11 m? What is the diameter of the sun?

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For very heavy object we use gravitational method.
For very light object we use mass spectrograph
1 AMU = Mass of 1/12 of C-12 atom
F
Measurement of Mass

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