An identity including an imaginary number, geometric constant, logarithmic constant, non-zero integer and zero.

A=(pi)*r^2

The area of a circle is related to the ratio pi and its radius squared.

F=ma

A force on an object is related to its mass and acceleration.

E=mc^2

Energy is related to mass and the speed of light.

T=2(pi)sqrt(L/g)

The period of a pendulum's swing is related to two pi and the square-root of the quotient of the length of the pendulum and the acceleration due to gravity.

a^2+b^2=c^2

The sum of the squares of the catheti (legs) of a right triangle are related to the square of its hypotenuse.

h=(gt^2)/2

The height of a falling object is related to time squared and half the acceleration due to gravity.

V=sqrt(3kT/m)

The velocity of a gaseous particle can be determined if the temperature and mass are known.