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

Problems 153

Summary

Now that you have reached this point in the text

• You should understand the importance of fundamental dimensions in engineering analy-
  sis. You should also understand what is meant by an engineering system and an engineer-
  ing component. You should also realize that physical laws are based on observation and
  experimentation.


• You should know the most common systems of units: SI, BG, and U.S. Customary.


• You should know how to convert values from one system of units to another.


• You should understand the difference between numerical and symbolic solutions.

6.1. Convert the information given in the accompanying

table from SI units to U.S. Customary units. Refer to

the conversion tables on the inside front and back cov-

ers of this book. Show all steps of your solutions. See

Examples 6.1 and 6.2.

6.3. The angle of twist for a shaft subjected to twisting

torque can be expressed by the following equation:

where

fthe angle of twist in radians

Tapplied torque (Nm)

Llength of the shaft in meter ( m)

Jshaft’s polar moment of inertia ( measure of

resistance to twisting)

Gshear modulus of the material (N/m

2

)

What is the appropriate unit forJ, if the preceding

equation is to be homogeneous in units?

6.4. Which one of the following equations is dimensionally

homogeneous? Show your proof.

a.Fma

b.

c. F(t 2 t 1 )m(V 2 V 1 )

d.FmV

e.

where

Fforce (N)

mmass (kg)

aacceleration ( m/s

2

)

Vvelocity ( m/s)

Rradius ( m)

ttime (s)

Fm

1 V 2 V 12

1 t 2 t 12

Fm

V

2

R

f

TL

JG

Problems

Convert from SI Units To U.S. Customary Units

120 km/h miles /h and ft /s

1000 W Btu /h and hp

100 m^3 ft^3

80 kg lbm

1000 kg /m

3

lbm/ft

3

900 N lbf

100 kPa lbf/in^2

9.81 m/s^2 ft /s^2

Convert from U.S.

Customary Units To SI Units

65 miles /h km/hr and m/s

60,000 Btu /h W

120 lbm/ft

3

kg /m

3

30 lbf/in^2 kPa

200 lbm kg

200 lbf N

6.2. Convert the information given in the accompanying

table from U.S. Customary units to SI units. Refer to

conversion tables on the inside front and back covers

of this book. Show all steps of your solutions. See

Examples 6.1 and 6.2.

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