Experimental Physics - 1

Science is all about experiments, all the hypothesis become a law only if they are justified experimentally. Experimentation involves lots of terms like accuracy, precision etc. and all the observations and corresponding values obtained are merely approximate, however the level of approximation depends upon the appartus. In this unit we will explore all about errors and then and then move on to another powerful tool called dimensional analysis. while closing the chapter we look at few experiment that are used to determine few physical quantities.

Conversion Table

Length:
1 in = 2.54 cm
1 m = 39.37
1 ft = 39.37 in. = 3.281 ft
12 in = 1 ft
3 ft = 1 yd
1 yd = 0.9144 m
1 km = 0.621 mi
1 mi = 1.609 km
1 mi = 5280 ft
1 = 10^-10m
1 m = 10^-6 ml = 10⁴
1 light-year = 9.461 x 10¹⁵

Area
1 m² = 10⁴ cm² = 10.76 ft²
1 ft² = 0.0929 m² = 144 in.²
1 in.² = 6.452 cm²

Volume
1 m³ = 10⁶ cm³ = 6.102 x 10⁴ in.³
1 ft³ = 1728 in.³ = 2.83 x 10^-2 m³
1 liter = 1000 cm³ = 1.0576 qt = 0.0353 ft³
1 ft³ = 7.481 gal = 28.32 liters = 2.832 x 10^-2 m³
1 gal = 3.786 liters = 281 in.³

Mass
1000 kg = 1 t(metric ton)
1 slug = 14.59 kg
1 u = 1.66 x 10^-27 kg
Force
1 N = 10⁵ dyne = 0.2248 Ib
1 Ib = 4.448 N
1 dyne = 10^-5N = 2.248 x 10^-6 Ib

Velocity
1 mi/h = 1.47 ft/s = 0.447 m/s = 1.61 km/h
1 m/s = 100 cm/s = 3.28 ft/s
1 mi/min = 60 mi/h = 88 ft/s

Acceleration
1 m/s² = 3.28 ft/s² = 100 cm/s²
1 ft/s² = 0.3048 m/s² = 30.48 cm/s²

Pressure
1 bar = 10⁵ N/m² = 14.50 Ib/in.²
1 atm = 760 mm Hg = 76.0 cm Hg
1 atm = 14.7 Ib/in.² = 1.013 x 10⁵ N/m²
1 Pa = 1 N/m² = 1.45 x 10^-4 Ib/in.²

Time
1 year = 365 days = 3.16 x 10⁷s
1 dy = 24 h = 1.44 x 10³ min = 8.64 x 10⁴ s

Energy
1 J = 0.738 ft.Ib = 10⁷ ergs
1 cal = 4.186 J
1 Btu = 252 cal = 1.054 x 10³ J
1 eV = 1.6 x 10^-19 J
931.5 MeV is equivalent to 1 u
1 kWh = 3.60 x 10⁶ J

Power
1 hp = 550 ft. Ib/s = 0.746 kW
1 W = 1 J/s = 0.738 ft.Ib/s
1 Btu/h 0.293 W

Physical Quantities:-
All the quantities by means of which we describe the laws of Nature and which can be measured are called physical quantities.

They are classified in to two parts:-

(a) Fundamental physical Quantity:- It is an elementary physical Quantity, which doesnot require any other physical quantity to express it. It is also known as basic physical quantity. They are length, mass , time, temperature, Electric current, Luminous intensity and amount of substance.

(b) Derived physical quantity:
All those physical quantities, which can be derived from the combination of two or more fundamental quantities or derived quantities. example velocity, density, force , energy etc.

UNITS
To measure a physical Quantity we require a standard of that physical quantity. This standard is called unit of that physical Quantity.

Dumb Question: Are units absolute things?
Ans:- Units are comperative when we mention any measurement, we actually give the comparitivity value of the quantity with respect to same internayionally fixed standard.

Fundamental Units:- The units of fundamental physical quantities are called fundamental units:

S. No.	Fundamental Physical Qty.	Units	Symbol
1. 2. 3. 4. 5. 6. 7.	Length Mass Time Electric Current Luminous Intensity Temperature Amount of Substance	metre kilogram second ampere canadela kelvin mole	m Kg s A Cd K mol