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880 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 881
Problem 5.28
A ball with a mass
mD0:25 kg
is dropped from rest from a height
h1D1:5
m
above an incline and rebounds off the incline at a height
h2D0:3
m above the
ground. After the rebound, the ball lands at a horizontal distance
dD5
m from
the point of contact between the ball and the incline. If the ball takes
0:57
s to
cover the distance
d
, and if the ball remains in contact with the incline for
0:01
s
during the rebound, determine the average force exerted by the incline onto the
ball during the rebound. Express the force using the component system shown.
Also, neglect the weight of the ball while it is in contact with the incline.
Solution
We begin by defining four time instant: t1D0is the time when the
882 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 883
Problem 5.29
A
1600 kg
car, when on a rectilinear and horizontal stretch of road and
when the tires do not slip, can go from rest to
100 km=h
in
5:5
s. Assum-
ing that the car travels on a straight stretch of road with a 40% slope and
that no slip occurs, determine how long it would take to attain a speed of
100 km=h
if the car were propelled by the same maximum average force
that can be generated on a horizontal road.
Solution
884 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 885
Problem 5.30
A
1600 kg
car, when on a rectilinear and horizontal stretch of road, can go from rest to
100 km=h
in
5:5
s.
(a)
Assuming that the car travels on such a road, estimate the average value of the force acting on the car
for the car to match the expected performance.
(b)
Recalling that the force propelling a car is caused by the friction between the driving wheels and the
road, and again assuming that the car travels on a rectilinear and horizontal stretch of road, estimate
the average value of the friction force acting on the car for the car to match the expected performance.
Also estimate the coefficient of friction required to generate such a force.
Solution
The calculation of the average magnitude of the force for Parts (a) and (b) is
the same. Hence, in either case, we model the car as a particle subject only to
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 887
Problem 5.31
A
51
8oz
baseball traveling at
80 mph
rebounds off a bat with a
speed of
160 mph
. The ball is in contact with the bat for roughly
103
s. The incoming velocity of the ball is horizontal, and the
outgoing trajectory forms an angle
˛D31ı
with respect to the
incoming trajectory.
(a) Determine the impulse provided to the baseball by the bat.
(b) Determine the average force exerted by the bat on the ball.
(c)
Determine how much the angle
˛
would change (with respect
to
31ı
) if we were to neglect the effects of the force of gravity
on the ball.
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.
888 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 889
Problem 5.32
In an unfortunate incident, a
2:75 kg
laptop computer is dropped onto the
floor from a height of
1
m. Assuming that the laptop starts from rest, that
it rebounds off the floor up to a height of
5cm
, and that the contact with
the floor lasts
103
s, determine the impulse provided by the floor to the
laptop and the average acceleration to which the laptop is subjected when
in contact with the floor (express this result in terms of
g
, the acceleration
of gravity).
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.
