Units and Dimensions - Physics formulas
1. Astronomical Unit
1AU= 1.5 × 10¹¹ m
2. Light Year
`1\ly=9.46\times10^{15}m`
3. Parsac
`1Parsac\=\3.07\times10^{16}m`
4. Vernier Calliper
Least Count = 1 MSD - 1 VSD
( MSD= Main Scale Division
VSD = Vernier Scale Division)
5. Least Count of Screw Guage
= Pitch / Number of divisions on circular scale
6. Error
i) Addition
Z = A + B
`\triangle Z=\triangle A+\triangle B`
ii) Subtraction
Z = A - B
`\triangle Z=\triangle A+\triangle B`
iii) Multiplication and Division
`\frac{\triangle Z}Z=\frac{\triangle A}A+\frac{\triangle B}B`
iv) If `\frac1Z=\frac1A+\frac1B`
`\frac{\triangle Z}{Z^2}=\frac{\triangle A}{A^2}+\frac{\triangle B}{B^2}`
7. Fundamental and Supplementary Units
| Fundamental Quantity | unit |
|---|---|
| Mass | Kilogram(Kg) |
| Length | Metre(m) |
| Time | Second(s) |
| Current | Ampere(A) |
| Temperature | Kelvin(K) |
| Amount of Substance | mole |
| Luminous Intensity | Candela(cd) |
| Supplementary Quantity | unit |
|---|---|
| Plane Angle | Radian(rad) |
| Solid Angle | Steradian(sr) |
8. Significant Figures
- All non-zero digits are significant.
- Zero between non zero digits is significant
- Leading Zeros are not significant.
- 0.000041 ➡ 2 significant figures.
- Trailing Zeros in a whole number (Without Decimal are not significant.
- Trailing zeros are significant if decimal is present.
- 0.00450 ➡ 3 significant figures.
- Exact numbers have infinite significant figures.