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PROBLEM 17.142 (Continued)
Panel in down position
22 2
panel 1
1
( ) (2 )[ (2 ) ]
Itbbb
(3)(24)
9
PROBLEM 17.143
Disks A and B are made of the same material and are of the same thickness;
they can rotate freely about the vertical shaft. Disk B is at rest when it is
dropped onto disk A, which is rotating with an angular velocity of 500 rpm.
Knowing that disk A has a mass of 8 kg, determine (a) the final angular
velocity of the disks, (b) the change is kinetic energy of the system.
B
222
0.15
11
22
BA
A
BBB
r
1
PROBLEM 17.143 (Continued)
PROBLEM 17.144
A square block of mass m is falling with a velocity
1
v
when it strikes a small
obstruction at B. Knowing that the coefficient of restitution for the impact between
corner A and the obstruction B is e 0.5, determine immediately after the impact
(a) the angular velocity of the block, (b) the velocity of its mass center G.
PROBLEM 17.144 (Continued)
Moments about A:
111 2
bbbb
mv I mev m
1
ev
1
3(1 ) sin 45
42 ev
1
3(1 ) cos 45
42 ev
ev
(0.5)
v
PROBLEM 17.145
A 3-kg bar AB is attached by a pin at D to a 4-kg square plate, which can rotate
freely about a vertical axis. Knowing that the angular velocity of the plate is
120 rpm when the bar is vertical, determine (a) the angular velocity of the plate
after the bar has swung into a horizontal position and has come to rest against pin
C, (b) the energy lost during the plastic impact at C.
10.083333 kg mI
Angular velocity. 1120 rpm 4 rad/s
Angular momentum about the vertical axis.
PROBLEM 17.146
A 1.8-lb javelin DE impacts a 10-lb slender rod ABC with a horizontal
velocity of v
0
30 ft/s as shown. Knowing that the javelin becomes
embedded into the end of the rod at Point C and does not penetrate very
far into it, determine immediately after the impact (a) the angular velocity
of the rod ABC after the impact, (b) the components of the reaction at B.
Assume that the javelin and the rod move as a single body after the
impact.
222
222
32.2 ft/s
11
(0.31056)(10) 2.5880 lb s ft
12 12
11
AC AC AC
ImL
1
22
2
5ft 2ft 3ft
(4.25 ft) (8 ft) 9.0588 ft
r
r
PROBLEM 17.146 (Continued)
Kinematics: (Rotation about B)
1
2
4.25 ft
AC
DE
vr
vr
Accelerations:
α
1
[
AD
ar
2
1
][r
]
2
() ()
0.74223 rad/s
WrImarImar
0.742 rad/sα
PROBLEM 17.146 (Continued)
(b) Components of reaction at B.
:Fma
WB][
W
][
mr
2
][
mr
][
mr
2
][
mr
y
PROBLEM 17.CQ1
A round object of mass m and radius r is released from rest at the top of a curved surface and rolls without
slipping until it leaves the surface with a horizontal velocity as shown. Will a solid sphere, a solid cylinder or
a hoop travel the greatest distance x?
(a) A solid sphere
(b) A solid cylinder
(c) A hoop
(d) They will all travel the same distance.
PROBLEM 17.CQ2
A solid steel sphere A of radius r and mass m is released from rest and rolls without slipping down an incline
as shown. After traveling a distance d the sphere has a speed v. If a solid steel sphere of radius 2r is released
from rest on the same incline, what will its speed be after rolling a distance d?
(a) 0.25 v
(b) 0.5 v
(c) v
(d) 2v
(e) 4v
