Human Power:
Breaking the brick with one hand requires concentration and it is one of the most efficient human
movements ever conceived. The key is to transfer more amount of force, in less time. The fastness matters in karate.
Power is a scalar quantity. The S.I. unit of power is the joule per second (J/s). This unit is used so often that it has a special name known as the watt (W), after James Watt, who greatly improved the rate at which steam engines could do work.
One watt (W) of power is expended when 1 joule of work is done in 1 second.If work is being done by a machine moving at speed v against a constant force, or resistance, F, then since work doe is force times distance, work done per second is Fv, which is the same as power.
For the same amount of work, power and time are inversely proportional. The power equation (Power = Work/Time) suggests that a more powerful engine can do the same amount of work in less time.
All machines are typically described by a power rating. The power rating indicates the rate at which that machine can do work upon other objects. Thus, the power of a machine is the work/time ratio for that particular machine.
Power reveals that a powerful machine is both strong (big force) and fast (big velocity). The powerful car engine is strong and fast. The powerful farm equipment is strong and fast. The powerful weight lifters are strong and fast. The powerful linemen on a football team are strong and fast.