Measurement of mass and time.

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Measurements of mass

• Mass is the basic property of matter.
• The mass is measured in kg in general.
• The smallest mass can be measured in amu.
• 1amu is the 1/12 mass of  the carbon Carbon atom.
• 1amu= 1.66*10^-27 kg.
• Small mass can be measured by mass spectroscopy.
• Larger mass can be calculated by the use of gravity.
• Range of mass is from 10^-30 kg the mass of electron to the 10^55 kg the mass of universe.

Measurements of time

• For measurements of time we need clock .
• We now use atomic standard of time.
• Atomic standard clock is based upon the vibration of cesium atom  that's why it is also called cesium clock or atomic clock.
• 1 second is defined as the 9,192,631,770 vibration of the radiation corresponding to the transition between the two hyperfine levels of the ground levels of cesium-133 atom.