This presentation tells you about the horrors of the non metric systems out there.

2. Difference Between Pound
Mass And Pound Force

3. Introduction
The fact that the imperial system of units has
the same unit name for both mass and force
related quantities can be quite confusing. Let us
shine some light on the difference between them.

4. Difference Between Mass And Force
The difference between mass and force can be
simply and effectively explained by the following
equation.
Force = mass*acceleration
Where force is defined as the product of mass and
acceleration.
Other common differences are of course also
present, like mass is the intrinsic property of
matter while force is an induced phenomena.
Simply put mass of an object is the amount of
matter an object contains within itself. Mass is
measured in kilograms in the metric system while
in the British engineering system it is measured
in pound mass.

5. Force can also be vaguely defined as weight of a
body because the weight of the body is the which
is pulling it downward towards the center of the
earth with the standard acceleration of 9.8ms^-2.
in the imperial system however 1lbf is the same
as 1lbm if the acceleration is 32.17ft/s^2. This
is of course a single case.