PROBLEM
14.5
A bullet is fired with a horizontal velocity of 500
mls
through a 3kg
T
block
A
and becomes embedded in a 2.5kg block
B.
Knowing that blocks
A
and
B
start moving with velocities of 3
mls
and 5
mis,
respectively
k
B
determine
(a)
the mass of the bullet,
(b)
its velocity as it travels from
~E;L,tJ
I
block
A
to block
B.
l~
SOLUTION
The masses are
m
for the bullet and
mA
and
mB
for the blocks.
(a)
The bullet passes through block
A
and embeds in block
B.
Momentum is conserved.
Initial momentum:
Final momentum:
Equating,
mAvA
+
mBvB
_
(3)(3) + (2.5)(5) = 43.434x 103kg
m=

Vo
vB
500  5
m
= 43.4g~
Initial momentum:
(b)
The bullet passes through block
A.
Momentum is conserved.
Final momentum:
Equating,
VI= mvo 
mAvA
= (43.434 x 103)(500)  (3)(3)
m
43.434 x 103
= 292.79
mls
VI
= 293
mls
~
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View Full DocumentPROBLEM
14.21
I
j
130~
In a game of pool, ball
A
is traveling with a velocity
v0 when it strikes
balls Band
C which are at rest and aligned as shown. Knowing that after
the collision the three balls move in the directions
indicated
and that
Vo
=
4
mls
and ve = 2.1
mis,
determine
the
magnitude
of the velocity
of
(a)
ball
A, (b)
ball
B.
.
SOLUTION
Velocity vectors:
Vo
=
Vo(cos300i + sin300j)
v
A
= V
A
(sin 7.4°i + cos 7.4°j )
VB=
VB
(sin 49.3°i  cos49.3°j)
ve
=
ve(cos45°i
+ sin45°j)
Conservation of momentum:
Divide
by
mA
=
mB
=
me
and substitute data.
4( cos300i + sin300j) =
vA
(sin 7.4°i + cos 7.4°j) +
VB
(sin 49.3°i

cos49.3°j)
+ 2.1( cos45°i + sin 45°j)
Resolve into components and rearrange.
i:
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 Summer '08
 staff
 Angular Momentum, Momentum, Velocity

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