adamkiewicz (ja28724) – Conservation of the energy – Morozova – (11102)
1
This
printout
should
have
14
questions.
Multiplechoice questions may continue on
the next column or page – find all choices
before answering.
001
10.0 points
Starting from rest at a height equal to the
radius of the circular track, a block of mass
16 kg slides down a quarter circular track
under the influence of gravity with friction
present (of coefficient
μ
).
The radius of the
track is 51 m.
The acceleration of gravity is 9
.
8 m
/
s
2
.
51 m
16 kg
θ
If the kinetic energy of the block at the
bottom of the track is 2600 J, what is the
work done against friction?
Correct answer: 5396
.
8 J.
Explanation:
W
=
W
f
+
K
W
f
=
m g R

K
= (16 kg) (9
.
8 m
/
s
2
) (51 m)

(2600 J)
=
5396
.
8 J
.
002
10.0 points
A spring with a force constant of 5.5 N/m has
a relaxed length of 2.62 m.
When a mass is
attached to the end of the spring and allowed
to come to rest, the vertical length of the
spring is 3.69 m.
Calculate
the
elastic
potential
energy
stored in the spring.
Correct answer: 3
.
14848 J.
Explanation:
Given:
k
= 5
.
5 N
/
m
x
= 3
.
69 m

2
.
62 m
= 1
.
07 m
Solution:
U
elastic
=
1
2
kx
2
=
1
2
(5
.
5 N
/
m)(1
.
07 m)
2
= 3
.
14848 J
003
(part 1 of 6) 10.0 points
A projectile of mass 0
.
522 kg is shot from
a cannon, at height 6
.
9 m, as shown in the
figure, with an initial velocity
v
i
having a
horizontal component of 5
.
9 m
/
s.
The projectile rises to a maximum height of
Δ
y
above the end of the cannon’s barrel and
strikes the ground a horizontal distance Δ
x
past the end of the cannon’s barrel.
Δ
x
v
i
57
◦
Δ
y
6
.
9 m
Determine the vertical component of the
initial velocity at the end of the cannon’s bar
rel, where the projectile begins its trajectory.
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 Spring '08
 moro
 Physics, Energy, Force, Mass, Velocity, Correct Answer, vxi

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