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PROBLEM 14.36
It is assumed that each of the two automobiles involved in the collision described in Problem 14.35 had been
designed to safely withstand a test in which it crashed into a solid, immovable wall at the speed v0. The
severity of the collision of Problem 14.35 may then be measured for each vehicle by the ratio of the energy it
absorbed in the collision to the energy it absorbed in the test. On that basis, show that the collision described
in Problem 14.35 is 2
(/)
AB
mm times more severe for automobile B than for automobile A.
PROBLEM 14.37
Solve Sample Problem 14.5, assuming that cart A is given an initial horizontal velocity
v
0
while ball B is at rest.
PROBLEM 14.38
Two hemispheres are held together by a cord which maintains a spring under
compression (the spring is not attached to the hemispheres). The potential
energy of the compressed spring is
120 J
and the assembly has an initial
velocity
0
v
of magnitude
08m/s.v
Knowing that the cord is severed when
30 ,
causing the hemispheres to fly apart, determine the resulting velocity
of each hemisphere.
PROBLEM 14.39
A 15-lb block B starts from rest and slides on the 25-lb wedge A, which is
supported by a horizontal surface. Neglecting friction, determine (a) the velocity
of B relative to A after it has slid 3 ft down the inclined surface of the wedge,
(b) the corresponding velocity of A.
PROBLEM 14.39 (Continued)
125 115
2 32.2 2 32.2 BA
2/
0.16741 22.5
BA
v
(a) /11.59 ft/s
BA v30
(b) (0.32476)(11.59)
A
v 3.76 ft/s
Av
PROBLEM 14.40
A 40-lb block B is suspended from a 6-ft cord attached to a 60-lb cart A,
which may roll freely on a frictionless, horizontal track. If the system is
released from rest in the position shown, determine the velocities of A and B
as B passes directly under A.
PROBLEM 14.40 (Continued)
Given data:
2
60 lb 40 lb, 6 ft
32.2 ft/s 25
AB
ww l
g
22
(2)(60) 1.2
AA
mw
PROBLEM 14.41
In a game of pool, ball A is moving with a velocity 0
v of magnitude
0
v 15 ft/s when it strikes balls B and C, which are at rest and aligned
as shown. Knowing that after the collision the three balls move in the
directions indicated and assuming frictionless surfaces and perfectly
elastic impact (that is, conservation of energy), determine the
magnitudes of the velocities ,
A
v ,
B
v and .
C
v
2
C
C
PROBLEM 14.42
In a game of pool, ball A is moving with a velocity 0
v of magnitude
v0 15 ft/s when it strikes balls B and C, which are at rest and aligned
as shown. Knowing that after the collision the three balls move in the
directions indicated and assuming frictionless surfaces and perfectly
elastic impact (that is, conservation of energy), determine the
magnitudes of the velocities vA, vB and vC.
PROBLEM 14.43
Three spheres, each of mass m, can slide freely on a frictionless, horizontal
surface. Spheres A and B are attached to an inextensible, inelastic cord of
length l and are at rest in the position shown when sphere B is struck
squarely by sphere C which is moving with a velocity 0.v Knowing that the
cord is taut when sphere B is struck by sphere C and assuming perfectly
elastic impact between B and C, and thus conservation of energy for the
entire system, determine the velocity of each sphere immediately after
impact.
