Download 13.67 The system shown is in equilibrium when f 5 0. Knowing that

Beer−Johnston−Cornwell:
Vector Mechanics for
Engineers: Dynamics,
Ninth Edition
13. Kinetics of Particles:
Energy and Momentum
Methods
209
© The McGraw−Hill
Companies, 2010
Text
Problems
13.67 The system shown is in equilibrium when f 5 0. Knowing that
797
initially f 5 90° and that block C is given a slight nudge when
the system is in that position, determine the speed of the block as
it passes through the equilibrium position f 5 0. Neglect the
weight of the rod.
D
1.1 ft
k = 600 lb/ft
A
f
B
C
25 lb
2.1 ft
0.3 ft
Fig. P13.67
13.68 A spring is used to stop a 50-kg package which is moving down a
2 m/s
20° incline. The spring has a constant k 5 30 kN/m and is held by
cables so that it is initially compressed 50 mm. Knowing that the
velocity of the package is 2 m/s when it is 8 m from the spring and
neglecting friction, determine the maximum additional deformation of the spring in bringing the package to rest.
50 kg
8m
13.69 Solve Prob. 13.68 assuming the kinetic coefficient of friction
between the package and the incline is 0.2.
Cable
20°
Fig. P13.68
13.70 A 300-g pellet is released from rest at A and slides with friction
along the surface shown. Determine the force exerted on the pellet by the surface (a) just before the pellet reaches B, (b) immediately after it has passed through B.
A
y
30°
r = 0.8 m
1.2
m
D
B
C
r = 6 in.
Fig. P13.70 and P13.71
B
13.71 A 300-g pellet is released from rest at A and slides without friction
along the surface shown. Determine the force exerted on the pellet by the surface (a) just before the pellet reaches C, (b) immediately after it has passed through C.
C
z
13.72 A 1.2-lb collar can slide without friction along the semicircular rod
BCD. The spring is of constant 1.8 lb/in and its undeformed length
is 8 in. Knowing that the collar is released from rest at B, determine (a) the speed of the collar as it passes through C, (b) the
force exerted by the rod on the collar at C.
12 in.
A
Fig. P13.72
3 in.
x