What is the physical significance of work?

[johncena]

As the title suggests, what is work? Or, what is the physical significance of work?
My textbook define work as crossproduct of force and displacement.
But why do we need that quantity?

 

[Dale]

It is the dot product of force and displacement, not the cross-product.

The reason that we need it is because of its fundamental relationship to energy which is very useful in simplifying many problems.

 

[schip666!]

I made up this little cheat sheet that I have to refer to every time I get involved in working out work. Understanding (and remembering) the dimensional analysis (the basic MKS units of each measure, e.g., Meters per Second is speed) should help in getting the idea of each unit.

                 Getting Energy Straight

Force -- Newton -- Mass times Acceleration ( F = MA )
                    Killograms times Meters per Sec^2: (Kg x M) / S^2
                    1 Newton = 10^5 dynes
                    1 pound-force ~= 4.5 Newtons

Work --  Joule  -- Force times Distance ( W = FD )
 (aka Energy)       Newtons times Meters -- N x M:     (Kg x M^2) / S^2
                    1 Joule = 10^7 ergs
                              .74 foot-pounds
                              6.25x10^18 electron volts
                    1 BTU = 1 Kilo-joule

                    note:
                     Watt = volt x ampere
                     1 Columb -- amp-sec ~= 6.25 x 10^18 electron-second
                     Watt-seconds -- volt x coulmb
                     1 Joule = 1 Watt-second
                     1 KwHr = 3.6 Mega-joule

Power -- Watt   -- Work per Time ( P = W/S )
                    Joules per Second -- J/S:          (Kg x M^2) / S^3
                    1 HP = 550 ft-lb/s = 745.7 watts
                    1 Kw = 1.34 HP
                    1 BTU/hour = .29 watts

for extra credit:
Pressure -- Pascal -- Force per Area ( P = F/A )
                       Newtons per Meter^2 -- N/M^2:    Kg / (M x S^2)
		        1 pound/sqin (PSI) = 6.9 Kpascal

 

[RonL]

I made up this little cheat sheet that I have to refer to every time I get involved in working out work. Understanding (and remembering) the dimensional analysis (the basic MKS units of each measure, e.g., Meters per Second is speed) should help in getting the idea of each unit.

                 Getting Energy Straight

Force -- Newton -- Mass times Acceleration ( F = MA )
                    Killograms times Meters per Sec^2: (Kg x M) / S^2
                    1 Newton = 10^5 dynes
                    1 pound-force ~= 4.5 Newtons

Work --  Joule  -- Force times Distance ( W = FD )
 (aka Energy)       Newtons times Meters -- N x M:     (Kg x M^2) / S^2
                    1 Joule = 10^7 ergs
                              .74 foot-pounds
                              6.25x10^18 electron volts
                    1 BTU = 1 Kilo-joule

                    note:
                     Watt = volt x ampere
                     1 Columb -- amp-sec ~= 6.25 x 10^18 electron-second
                     Watt-seconds -- volt x coulmb
                     1 Joule = 1 Watt-second
                     1 KwHr = 3.6 Mega-joule

Power -- Watt   -- Work per Time ( P = W/S )
                    Joules per Second -- J/S:          (Kg x M^2) / S^3
                    1 HP = 550 ft-lb/s = 745.7 watts
                    1 Kw = 1.34 HP
                    1 BTU/hour = .29 watts

for extra credit:
Pressure -- Pascal -- Force per Area ( P = F/A )
                       Newtons per Meter^2 -- N/M^2:    Kg / (M x S^2)
		        1 pound/sqin (PSI) = 6.9 Kpascal

Thanks, this might prove very helpful to me.

Ron

 

[PJC01]

The physical significance of work is that it represents the amount of energy transferred to or from a system as a result of a force acting over a certain distance. This means that work is a measure of the effort required to move an object or cause a change in its state. In scientific terms, work is defined as the product of the force applied to an object and the distance over which the force acts, with the direction of the force and the displacement being perpendicular to each other.

In practical terms, work is an important concept in understanding and analyzing physical systems. It allows us to quantify the amount of energy used or produced in various processes, such as lifting an object, pushing a car, or even the beating of our own hearts. Work also helps us understand the efficiency of machines and processes, as well as the conservation of energy in different scenarios.

Furthermore, the concept of work is crucial in the field of mechanics, where it is used to calculate the amount of force required to move an object, or the distance an object can travel given a certain amount of force. It is also essential in fields such as thermodynamics, where it is used to analyze the transfer of energy in different systems.

In summary, the physical significance of work lies in its ability to quantify the energy transfer in various physical processes, making it a fundamental concept in the study of mechanics and other branches of science.