# Physics formulae for beginners

Essay by lil_azn77 May 2006

Electrical energy in the home

E = F/q

E = electric field strength

F = force

q = charge

E = kq/r2

E = electric field strength

k = 9.00 x 109

q = charge

r = separation of charges

F = Eq

F = force

E = electric field strength

q = charge

R = V/I

R = resistance

V = potential drop

I = current

R = kl/A

R = resistance

k =

P = VI (P = V2/R or P = I2R)

P = Power

V = Voltage rise

I = Current

R = resistance

W = VIt

W = Energy

V = Voltage rise

I = current

t = time

vav = ÃÂr/ ÃÂt

vav = average velocity

ÃÂr = displacement (change in position)

ÃÂt = time

aav = ÃÂv/ ÃÂt

ÃÂv = the change in velocity

ÃÂt = time interval

When t = 0, the velocity is u

Thus: aav = v-u/t

Where v is the velocity at time t.

v - u = at

v = u + at

F = ma

W - air resistance = ma

When dense objects fall through small distances near the surface of the Earth it is usually quite reasonable to assume that the air resistance is negligible. Thus:

W = ma

mg = ma (where g is the gravitational field strength)

g = a

W = weight

m = mass

F = mv2/r

F = centripetal force (the net force on an object traveling in a circular path at constant speed. It is directed towards the centre of the circle)

m = mass

v = constant speed

Ek = 1/2mv2

Ek = kinetic energy

m = mass

v = speed

W = Fs

W = work

F = magnitude of force

s = displacement in the direction of the force

p = mv

p = momentum

m = mass of object

v = velocity

I = Ft

I = impulse

F = force

t = time

V = W/Q

V = potential difference in volts

W = work done by field in joules

Q = charge being pushed in coulombs