P = W/t is the formula to determine power. Power equals work done divided by the time it took to do that work. The International System of Units (SI) defines power as the rate at which work is done, or the rate energy is expended.
The watt is the SI unit for power. Both mechanics and electricity use the term watt. It links the two together. A watt equals one joule of work per second of time. One watt is also the power of a current of one ampere flowing through the electrical potential of one volt. The term watt is in honor of James Watt, a British engineer.
Joule is the SI unit of work or energy. A joule is the amount of energy to move a newton one meter. A newton is a standard unit of work. It is the amount of energy to accelerate one kilogram one meter per second per second. The joule, pronounced "jewel," gets its name after James Prescott Joule. One of his experiments in 1843 showed thermal and mechanical energy as being equivalent.
A calorie is the amount of heat required to raise one kilogram of water 1 degree Celsius at sea level. This unit is the large calorie. The small calorie is the amount of heat required to raise one gram of water 1 degree Celsius, from 14.5 degrees C to 15.5 degrees, at sea level. This is equal to 4.1868 joules or 0.00396832 BTU.
The British thermal unit is the amount of heat required to raise one pound of water 1 degree Fahrenheit. This is also called the heat unit in the United States and Britain. One BTU is approximately 1.055056 kilojoules or 0.293071 watt-hour.
The SI unit of force is the newton. A newton is the force that accelerates one kilogram one meter per second per second. It is in honor of Sir Isaac Newton, the scientist and mathematician. He was the first to understand the relationship between force, mass and acceleration.