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426 Solutions Manual
of McGraw-Hill, and must be surrendered upon request of McGraw-Hill. Any duplication or distribution, either in print or electronic form, without the
permission of McGraw-Hill, is prohibited.
Dynamics 2e 427
Problem 3.17
A vehicle is stuck on the railroad tracks as a
430;000 lb
locomotive is approaching with a speed of
75 mph
.
As soon as the problem is detected, the locomotive’s emergency brakes are activated, locking the wheels
and causing the locomotive to slide.
Continue Prob. 3.16 and determine the time required to stop the locomotive.
Volvo
of McGraw-Hill, and must be surrendered upon request of McGraw-Hill. Any duplication or distribution, either in print or electronic form, without the
permission of McGraw-Hill, is prohibited.
of McGraw-Hill, and must be surrendered upon request of McGraw-Hill. Any duplication or distribution, either in print or electronic form, without the
permission of McGraw-Hill, is prohibited.
Dynamics 2e 429
Problem 3.18
As the skydiver moves downward with a speed
v
, the air drag exerted by the parachute on the skydiver has
a magnitude
FdDCdv2
(
Cd
is a drag coefficient) and a direction opposite to the direction of motion.
Determine the expression of the skydiver’s acceleration in terms of
Cd
,
v
, the mass of the skydiver
m
, and
the acceleration due to gravity.
Solution
We model the skydiver as a particle moving only in the vertical direction.
We assume that the forces acting on the skydiver are only gravity and the air
430 Solutions Manual
Problem 3.19
A car is driving down a
23ı
rough incline at
55 km=h
when its brakes
are applied. Treating the car as a particle and neglecting all forces
except gravity and friction, determine the stopping distance if
(a)
The tires slide and the coefficient of kinetic friction between the
tires and the road is 0:7.
(b)
The car is equipped with antilock brakes and the tires do not slide.
Use
0:9
for the coefficient of static friction between the tires and
the road.
Solution
of McGraw-Hill, and must be surrendered upon request of McGraw-Hill. Any duplication or distribution, either in print or electronic form, without the
permission of McGraw-Hill, is prohibited.
432 Solutions Manual
Problem 3.20
The truck shown is traveling at
v0D60 mph
when the driver
applies the brakes to come to a stop. The deceleration of the
truck is constant, and the truck comes to a complete stop after
braking for a distance of
350 ft
. Treat the crate as a particle so
that tipping can be neglected.
Determine the minimum coefficient of static friction between
the crate
A
and the truck so that the crate does not slide relative
to the truck.
Solution
Using the information provided we first determine the (constant) acceleration of the truck.
This acceleration is also that of the crate (the crate does not slip relative to the truck) and
Dynamics 2e 433
Problem 3.21
The truck shown is traveling at
v0D60 mph
when the driver
applies the brakes to come to a stop. The deceleration of the
truck is constant, and the truck comes to a complete stop after
braking for a distance of
350 ft
. Treat the crate as a particle so
that tipping can be neglected.
If the coefficient of kinetic friction between the crate
A
and
the bed of the truck is
0:3
and static friction is not sufficient to
prevent slip, determine the minimum distance
d
between the
crate and the truck Bso that the crate never hits the truck at B.
of McGraw-Hill, and must be surrendered upon request of McGraw-Hill. Any duplication or distribution, either in print or electronic form, without the
permission of McGraw-Hill, is prohibited.
434 Solutions Manual
of McGraw-Hill, and must be surrendered upon request of McGraw-Hill. Any duplication or distribution, either in print or electronic form, without the
permission of McGraw-Hill, is prohibited.
Dynamics 2e 435
Problem 3.22
The truck shown is traveling at
v0D60 mph
when the driver
applies the brakes to come to a stop. The deceleration of the
truck is constant, and the truck comes to a complete stop after
braking for a distance of
350 ft
. Treat the crate as a particle so
that tipping can be neglected.
If the coefficient of kinetic friction between the crate
A
and
the bed of the truck is
0:3
, static friction is not sufficient to prevent
slip, and the distance
d
from the front of the crate to the truck at
B
is
10 ft
, determine the speed relative to the truck with which
the crate strikes the truck at B.
Solution
of McGraw-Hill, and must be surrendered upon request of McGraw-Hill. Any duplication or distribution, either in print or electronic form, without the
permission of McGraw-Hill, is prohibited.
