Foot-pound force
In physics, a foot-pound force (symbol ft·lbf) is most of the time incorrectly abbreviated to foot-pounds, is from the English Engineering System and U.S. customary unit of mechanical work, or energy, although in scientific fields one commonly uses the equivalent metric unit of the joule (J). There are approximately 1.356 J/ft·lbf, or exactly 1.355 817 948 331 400 4 J/ft·lbf. It is also called a dynam.
Unit of work or energy
To calculate a foot-pound force, you can use this formula,
- W = F × d or transitional kinetic energy = F * d
where W is work (in foot-pound force), F is force (in [[pound force), and d is distance (in feet) over which the force is applied (measured in the direction of the force).
Other energy equivalents are: 1 ft-lbf is equal to; 1.355818 Newton meters (Nm), .001285 British Thermal Units (Btu) and .323832 Calories. Also there are "power" equivalents: 1 ft-lbf/sec. is equal to; 550 Horsepower (hp/sec.), 778 British Thermal Units (Btu/sec.) and 4.184 Watts (w).
Origins of foot-pound force
Foot-pound force is derived from the original equation of KE = wz. Where as KE is Kinetic energy, w is the weight of the body and z is the average velocity of the falling body times the time of that fall.
These are the factors for w.
w = m*g/gc
Where as w is weight, m is mass, g is the local acceleration of gravity and gc is the dimensional constant.
These are the factors for z.
z=1/2*v*t
Where as z is the average velocity of the falling body times the time of the fall, ½ is the coefficient to find the average velocity, v is the velocity and t is the time of fall.
When wz is fully factored to its four UOM (Units of measure)than reduced, the two remaining factors left are F and d. With these two variables left, this proves mathematically that energy of motion is force through distance, as in the original experiment of the two falling objects; force though distance
The four UOM are F [Force (pound force)], d [distance (foot)], m [ mass (pound mass)], t [ time (second).]
Unit of torque
The foot-pound force is also the unit of torque, which is conventionally expressed in SI units as newton-meters rather than joules. Sometimes the order of the units is reversed for torque, expressed as poundral rather than foot-pound force.
Strictly speaking, foot pound is a different unit, having the dimensions of length×mass, rather than the foot-pound force's length×mass×acceleration, but it has few applications, which is why the abbreviation of "foot-pound force" to "foot pound" is rarely a problem.