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www.pearsoneducation.net/hibbelerfollowing the links to Engineering Mechanics: Statics,
Twelfth Edition text.
1 General principles
1-1.Redondee los siguientes números a tres cifras significa- tivas: (a) 4.65735 m, (b) 55.578 s, (c) 4555 N y (d)
2768 kg.
Solution:
4.65735 m = 4.66 m.
(b) 55.578 s= 55.6 s.
(c) 4555 N = 4.56 x 10^3 = 4.56 kN.
2768 kg = 2.77 x 10^3 = 2.77 Mg.
1-2.Represent each of the following combinations of units in the correct SI form with a prefix
adecuado: (a)μMN, (b) N>μm, (c) MN>ks2y (d) kN>ms.
Solution:
(a) μMN=N.
(b) N/μm=MN/m.
(c) MN/ks2= N/s2
(d) kN/ms=MN/s.
1-3.Represente cada una de las siguientes cantidades en la forma correcta del SI con un prefijo adecuado: (a)
0.000431 kg, (b) 35.3(103N y (c) 0.00532 km.
Solution:
0.000431 kg = 0.431 g.
(b) 35.3(10335300N = 53.3kN
0.00532 km = 5.32 m.
Mg/ms
(b) N/mm y (c) mN/(kg*μs).
Solution:
(a) Mg/ms=1000000g/0.001s*1kg/1000g=1000kg/0.001s=1000000kg/s=Mkg/s.
(b) N/mm = 1N/mm * 1000mm/1m = 1000N/m = kN/m.
(c) mN/(kg*μs)=0.001N/(1kg*0.000001s)=1000N/(kg*s)= kN/(kg*s)
1-5. Represent each of the following combinations of units in the correct SI form with a prefix
adecuado: (a) kN/μs, (b) Mg/mN, (c) MN/(kg*ms).
Solution:
(a) kN/μs=1000 N/0.000001 s = 1X10^9N/s=GN/s.
(b) Mg/mN=1000000g/0.001N*(1kg/1000g)=1000000kg/N=Mkg/N=Gg/N.
(c) MN/(kg*ms)=1000000N/(kg*0.001s)=GN/(kg*s).
1-6. Represent each of the following expressions with three significant figures and write each answer in
unidades SI con un prefijo adecuado: (a) 45 320 kN, (b) 568(105) mm y (c) 0.005 63 mg.
Solution:
45 320 kN = 45320000 N = 45.3 MN.
(b) 568(10556800000 mm = 56.8 km.
0.00563 mg = 0.00000563 g = 5.63 μg.
A rocket has a mass of 2503slugs on Earth. Specify (a) their mass in SI units and (b) their
weight in SI units. If the rocket is on the Moon, where the acceleration due to gravity is gL5.30 feet/second2,
use three significant figures to determine your weight in SI units
Solution:
its mass in SI units
m=250000 slug * 14.59 kg / 1 slug = 3647500000 g = 3.65 Gg.
(b) its weight in SI units.
W = m * g T = 3647500 kg * (9.81 m/s^2) = 35781975 N = 35.8 MN
(c) its weight in SI units
gL = 5.3 ft/s^2 * (0.3048 m/1 ft) = 1.61544 m/s^2
W = m * g = 3647500 kg * (1.61544 m/s^2) = 5892317400 N = 5.89 MN
its mass in SI units.
m = W / gL = 5892317400 N / (1.61544 m/s^2) = 3647500000 g = 3.65 Gg
*1-8.Si un automóvil viaja a 55 mi/h, determine su velocidad en kilómetros por hora y metros por segundo.
Solution:
The speed in kilometers per hour is:
55 mi/h * 5280 feet/1 mi * 0.3048 m/1 foot * 1 km/1000 m = 0.000003175 km/h = 3.18 μkm/h.
The speed in meters per second is;
0.000003175 km/h * 1000 m/1 km * 1 h/60 s = 0.00005291666667 m/s
1-9. Pascal (Pa) is actually a very small unit of pressure. To demonstrate this, convert 1 Pa = 1
N/m2a lb/pie2The atmospheric pressure at sea level is 14.7 lb/inch.2How many pascals does this equal?
Solution:
If 1 lb = 4,448 N
1 Pa = 1 N/m2a lb/pie2
1 N/m21 lb/4,448N * (0.3048m)2/1pie20.02088647482014 lb/foot220.09 x 10-3lb/pie2
The atmospheric pressure at sea level is 14.7 lb/inch.2
14.7 lb/inch24,448 N/1 lb 1 inch20.0254m2101347.88 N/m2=101347.88 Pa=101 kPa=1 Atm
1-10.¿Cuál es el peso en Newtons de un objeto que tiene una masa de: (a) 10 kg, (b) 0.5 g y (c) 4.50 Mg?
Express the result with three significant figures. Use an appropriate prefix.
(a) 10 kg*9.81 m/s^2 = 98.1 N
0.5 g * 1 kg / 1000 g * 9.81 m/s^2 = 0.004905 N = 4.90 nN
4.50 Mg = 4500000 g * 1 kg / 1000 g * 9.81 m/s^2 = 44145 N = 44.1 kN
1-11. Carry out each of the following operations and express the answer with three significant figures, use
354 mg(45 km)/(0.0356 kN)
y (c) 435 MN/23.2 mm.
(a) 354 mg(45 km)/(0.0356 kN)
0.354kg*45000m/(35.6N)= 447.47191011236g*m/N=0.447kg*m/N
(0.004 53 Mg)(201 ms)
(4,530kg)(0,201 ms)= 0.91053kg*s=0.911kg*s
(c) 435 MN/23.2 mm.
435000000 N/0.0232 m=18750000000 N/m=18.8 GN/m
The specific weight (weight/volume) of brass is 520 lb/ft³.3Determine its density (mass/volume) in
SI units. Use an appropriate prefix.
520 lb/pie34,448N/lb 1 pie3(0.3048m)3= 7588.45144356955315 N/m3
Density mass volume = (7588.45144356955315 N / 9.81 m/s²2) / m3=773.54245092452122 kg/m3
Density mass/volume=773 kg/m3
1-13.Realice cada una de la siguientes conversiones con tres cifras significativas: (a) 20 lb*pie a N*m, (b) 450
lb/pie3a kN/m3y (c) 15 feet/hour to mm/s.
Solution:
(a) 20 lb*pie a N*m,
20 lb * π * 4.448 N / 1 lb * 0.3048 m / 1 π = 27.115008 N*m = 27.1 N*m
450 lb/foot3a kN/m3
450 lb/pie34,448 N/1 lb *1 pie3(0.3048m)370685.83690973156225 N/m370.7 kN/m3
15 feet/hour to mm/s
1-14. The density (mass/volume) of aluminum is 5.26 slug/foot.3Determine its density in SI units.
Use an appropriate prefix.
Solution:
( )
The water has a density of 1.94 slug/foot.3What is its density expressed in SI units? Express it
response with three significant figures.
Solution:
( )
1-16. Two particles have a mass of 8 kg and 12 kg, respectively. If they are separated by a distance of
800 mm, determine the gravitational force acting between them. Compare this result with the weight of each.
particle.
Solution:
where
F = gravitational force between the two particles
G = universal gravitational constant; according to experimental evidence, G = 66.73(10-12)
m3/(kg*s2)
m1,m2mass of each of the two particles
r = distance between the two particles
Known variables;
G=66.73(10-12) m3/(kg*s2)
m18kg
212kg
r=0.8m
( )
( )
Determine the mass in kilograms of an object that has a weight of 20 mN.
Express the answer with three significant figures.
Solution:
How ,
Where,
W=weight
m=mass
9.81 m/s
20 mN
20 mN = 0.020 N, solving for mass I have
150 kN
60 MN
1-18. Evaluate each of the following operations and express the answer in SI units with three significant figures.
significant; use the appropriate prefix: (a) (200 kN)2(b) (0.005 mm)2y (c) (400 m)3.
Solution:
(200 kN)2,
( )
( )
( )
(0.005 mm)2y
( )
( )
( )
(c) (400 m)3.
( )
( )
( )
1-19. Use the base units of the SI system to show that equation (1-2) is dimensionally
homogeneous and gives a value of Fen newtons. Determine the gravitational force with three significant figures.
that acts between two spheres that touch each other. The mass of each sphere is 200 kg and its radius is 300
mm.
Solution:
equation (1-2)
I determine the gravitational force
( )
m1=200 kg=m2
r=600mm=0.6m
( )
1-20.Perform each of the following operations and express the answer with three significant figures, in
0.0735 Mm/kg2y (b) (35 mm)248 kg3.
(0.631 Mm)/(8.60 kg)2y
( )
(b) (35 mm)248 kg3.
( )
( )
( )
the given operation would be
( )
0.0256 kg/m
IF with an appropriate prefix.