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Assignment #9
Due: 11:00pm on Tuesday, July 23, 2013
You will receive no credit for items you complete after the assignment is due.
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***** Note: this assignmnet is due on MONDAY March 10 *****
A Bullet Is Fired into a Wooden Block
A bullet of mass
is fired horizontally with speed
at a wooden block of mass
resting on a frictionless table. The
bullet hits the block and becomes completely embedded within it. After the bullet has come to rest within the block, the block,
with the bullet in it, is traveling at speed
.
Part A
Which of the following
best
describes this collision?
Hint 1.
Types of collisions
An inelastic collision is a collision in which kinetic energy is not conserved. In a
partially
inelastic collision, kinetic
energy is lost, but the objects colliding do not stick together. From this information, you can infer what completely
inelastic and elastic collisions are.
ANSWER:
Correct
m
b
v
i
m
w
v
f
perfectly elastic
partially inelastic
perfectly inelastic
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View Full DocumentPart B
Which of the following quantities, if any, are conserved during this collision?
Hint 1.
When is kinetic energy conserved?
Kinetic energy is conserved only in perfectly elastic collisions.
ANSWER:
Correct
Part C
What is the speed of the block/bullet system after the collision?
Express your answer in terms of
,
, and
.
Hint 1.
Find the momentum after the collision
What is the total momentum
of the block/bullet system after the collision?
Express your answer in terms of
and other given quantities.
ANSWER:
Hint 2.
Use conservation of momentum
The momentum of the block/bullet system is conserved. Therefore, the momentum before the collision is the
same as the momentum after the collision. Find a second expression for
, this time expressed as the total
momentum of the system before the collision.
Express your answer in terms of
and other given quantities.
ANSWER:
ANSWER:
kinetic energy only
momentum only
kinetic energy and momentum
neither momentum nor kinetic energy
v
i
m
w
m
b
p
total
v
f
=
p
total
(
+
)
m
w
m
b
v
f
p
total
v
i
=
p
total
m
b
v
i
Correct
A OneDimensional Inelastic Collision
Block 1, of mass
= 5.50
, moves along a frictionless air track with speed
= 15.0
. It collides with block 2, of
mass
= 13.0
, which was initially at rest. The blocks stick together after the collision.
Part A
Find the magnitude
of the total initial momentum of the twoblock system.
Express your answer numerically.
Hint 1.
How to approach the problem
Find the initial momentum of each block separately; then add the two momenta together. Recall that momentum
is equal to mass times velocity:
.
ANSWER:
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 Summer '13
 Ellison
 Physics

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