Engineering Fundamentals: An Introduction to Engineering, 4th ed.c

And the relationship between the degree Rankine and the Kelvin by:

We will explore these relationships further in Chapter 11.

U.S. Customary Units

In the United States, most engineers still use the U.S. Customary system of units. The unit of

length is a foot (ft), which is equal to 0.3048 meter; the unit of mass is a pound mass (lbm),

which is equal to 0.453592 kg; and the unit of time is a second (s). In U.S. Customary system,

the unit of force is pound force (lbf) and 1 lbfis defined as the weight of an object having a mass

of 1 lbmat sea level and at a latitude of 45, where acceleration due to gravity is 32.2 ft /s

2

. One
pound force is equal to 4.448 newton (N). Because the pound force is not defined formally
using Newton’s second law and instead is defined at a specific location, a correction factor must

T 1 °R 2 

9

5

T 1 K 2

136 Chapter 6 Fundamental Dimensions and Units

TABLE 6.3 Examples of Derived Units in Engineering

Name of Symbol for Expression in Terms

Physical Quantity SI Unit SI Unit of Base Units

Acceleration m/s

2

Angle Radian rad

Angular acceleration rad /s

2

Angular velocity rad /s

Area m

2

Density kg /m

3

Energy, work, heat Joule J Nm or kgm

2

/s

2

Force Newton N kgm/s

2

Frequency Hertz Hz s

 1

Impulse NS or kgm/s

Moment or torque Nm or kgm

2

/s

2

Momentum kgm/s

Power Watt W J/s or Nm/s or kgm

2

/s

3

Pressure, stress Pascal Pa N/m

2

or kg /ms

2

Velocity m/s

Volume m

3

Electric charge Coulomb C As

Electric potential Volt V J/C or m

2

kg /(s

3

A

2

)

Electric resistance Ohm  V/A or m

2

kg /(s

3

A

2

)

Electric conductance Siemens S 1/  or s

3

A

2

/( m

2

kg)

Electric capacitance Farad F C / V or s

4

A

2

/( m

2

kg)

Magnetic flux density Tesla T Vs/m

2

or kg /(s

2

A)

Magnetic flux Weber Wb Vs or m

2

kg /(s

2

A)

Inductance Henry H Vs/A

Absorbed dose of radiation Gray Gy J/ kg or m

2

/s

2

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