Physics for computer sciences: lecture1 Dr. Lobna Mohamed Abou El-Magd

Classical physics includes the principles of classical mechanics thermodynamics Optics electromagnetism

modern physics : includes the theories of relativity not only correctly describes the motion of objects moving at speeds comparable to the speed of light; it also completely modifies the traditional concepts of space, time, and energy shows that the speed of light is the upper limit of the speed of an object and that mass and energy are related. The quantum mechanics. descriptions of physical phenomena at the atomic level

Temperature- electric current - luminous intensity - the amount of substance (kelvin) (ampere) ( candela) (mole). Standards of Length, Mass, and Time the SI (Système International) fundamental units of length, mass, and time a the meter kilogram second

the U.S. customary system fundamental units of length, mass, and time foot (ft) slug second

Dimensional Analysis It denotes the physical nature of a quantity. dimensions of length, mass, and time are L M T the dimensions of speed [v] = L/T= L T -1. the dimensions of area [A] = L 2 General form :L a M b T c

EXAMPLES Analysis of an Equation Show that the expression v = at, is dimensionally correct. where v represents speed a acceleration t an instant of time, If the expression were given as v =t 2, it would be dimensionally incorrect

EXAMPLES Suppose we are told that the acceleration a of a particle moving with uniform speed v in a circle of radius r is proportional to some power of r, say r n, and some power of v, say v m. Determine the values of n and m and write the simplest form of an equation for the acceleration.

EXAMPLES The wavelength λ of the wave depends on the speed v of the wave and its frequency f. knowing that [λ]=[L] [v]=[L][T] -1 [f]= [T] -1, decide which of the following equations is correct, λ= vf or λ=v/f.