Physical Quantities Flashcards
Physical quantities
All measurable quantities are called physical quantities.
Base quantities
Base quantities are not defined in terms of other physical quantities. The base quantities are the minimum number of those physical quantities in terms of other physical quantities can be defined.
Base units
Units for measuring base quantities
Derived units
Units for measuring derived quantities
Radian
Radian is the plane angle between two radii if a circle which cut off on the circumference an arc, equal in length to the radius
Steradian
The steradian is the solid angle subtended at the centre of a sphere by an area of its equal to the square of radius of the sphere
Types of errors
Random error
Systematic error
Random error
Random error occurs when repeated measurement of the quantity give different values under the same condition.
Systematic error
Error due to incorrect design or calibration of the measuring device.
How to recover random error
Repeating the measurement several times and taking an average can reduce the effect of random errors.
How to recover systematic error
Systematic error can be reduced by comparing the instruments with another which is known to be more accurate or by applying a correction factor
Significant figures
In any measurement, all the accurately known digits and first doubtful digit
Precision
A precise measurement is the one which has less absolute uncertainty
Accuracy
An accurate measurement is the one which has less fractional or percentage uncertainty.
Time taken by light to travel from moon to earth
1 min 20s
