# HW # 15 WINTER BREAK PACKET

Urban and Civil

Nov 15, 2013 (4 years and 6 months ago)

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Name:

Class Period:

(2 points each)

1.

Which of these graphs shows constant energy?

2.

Which of these graphs shows the initial energy
the same as the final energy?

3.

In graph C, describe wha
t happens to the kinetic
energy as the time increases.

4.

In graph B, what is the Kinetic Energy when
time is at ½ t?

5.

Which graph (or part of graph) shows an
increase in Kinetic Energy?

Use the following data tables
tic and Potential Energy

(
2 points each)

Data Table I

Data Table II

1.

What was the control in the experiment?

2. What materials would need to be used to collect this data?

3. According to Data Table I, when the height was at a maxi
mum, what was the Potential Energy?

4. Predict what the Kinetic Energy would be at a velocity of 3.09.

5.

Develop a conclusion for the relationship between Height and Potential Energy?

HW # 15

WINTER BREAK PACK
ET

s

Superconductivity is the ability of certain materials to conduct electrical current with no resistance and extremely low loss
es. This
ability to carry large amounts of current can be applied to electric power devices such as motors and generators, and to

electricity
transmission in power lines. For example, superconductors can carry as much as 100 times the amount of electricity of ordinar
y
copper or aluminum wires of the same size.

Scientists had been intrigued with the concept of superconductivity sin
ce its discovery in the early 1900s, but the extreme low
temperatures the phenomenon required was a barrier to practical and low
-
cost applications. This all changed in 1986, when a new
class of ceramic superconductors was discovered that "superconducted" a
t higher temperatures. The science of high
-
temperature
superconductivity (HTS) was born, and along with it came the prospect for an elegant technology that promises to "supercharge
" the
way energy is generated, delivered, and used.

1.
According to the pa
ssage,
what discovery
enable
d

superconductivity to become a more practical energy source which can be
utilized outside of the laboratory?

2. When was superconductivity first discovered?

3.
In which of the following publication types would this articl
e most likely appear in?

a. A scholarly journal read by specialists and scientists who work directly with superconductivity

b. A modern science magazine intended for leisure reading

c. A book chapter in an advanced chemistry textbook

d. A magazine inten
ded to be dispersed at home craft fairs

4. According to the passage, what is the definition of superconductivity?

5.

How much electricity can superconductor wires carry when compared to ordinary copper or aluminum wires?

Energy can be in one of two states: potential or kinetic. Energy can be transferred from potential to kinetic and between obj
ects.
Potential energy is stored energy

energy ready to go. A lawn mower filled with gasoline, a
car on top of a hill, and students waiting
to go home from school are all examples of potential energy. Water stored behind a dam at a hydroelectric plant has potential

energy. Most of the energy under our control is in the form of potential energy. Poten
tial energy can be viewed as motion waiting to
happen. When the motion is needed, potential energy can be changed into one of the six forms of kinetic energy. Kinetic ene
rgy is
energy at work. A lawn mower cutting grass, a car racing down a hill, and stu
dents running home from school are examples of
kinetic energy. So is the light energy emitted by lamps. Even electrical energy is kinetic energy. Whenever we use energy to
do
work, it is in the kinetic state.

1. What are the units of
Potential Energy and
Kinetic Energy?

2.
The

greate
st potential
energy is at what height?

3. The
greatest

kinetic energy is at what height?

4.
According to the reading passage, how is potential energy defined?

5.

According to the reading passage, what are examples of kinetic energy?

Mass (g)

Height (m)

Potential Energy (J)

Kine
tic Energy (J)

Ball 1

10

0

0

2000

10

10

1000

1000

10

20

2000

0

Ball 2

20

0

0

4000

20

10

2000

2000

20

20

4000

0

Ball 3

50

0

0

10000

50

10

5000

5000

50

20

10000

0

1.
How much work (energy) is needed to lift an object that weighs 200 N to a height of 4 m?

2. On his way off to college, Russell drags his suitcase 15.0 m from the door of his house to the car at a constant speed wit
h a
horizontal force of 95.0 N. How mu
ch work does Russell do to overcome the force of friction?

3. Marissa does 3.2 J of work to lower the window shade in her bedroom a distance of 0.8 m. How much force must Marissa exert

on

4. Atlas and Hercules, two carnival sidesh
ow strong men, each lift 200.
-
kgbarbells 2.00 m off the ground. Atlas lifts his barbells in 1.00 s
and Hercules lifts his in 3.00 s.

a) Which strong man does more work? b) Calculate which man is more powerful.

5. Legend has it that Isaac Newton “disco
vered” gravity when an apple fell from a tree and hit him on the head. If a 0.20
-
kg apple fell
7.0 m before hitting Newton, what was its change in PE during the fall?

6. A greyhound at a race track can run at a speed of 16.0 m/s. What is the KE of a 20
.0
-
kg greyhound as it crosses the finish line?

7. In a wild shot, Bo shoots a pool ball of mass m off a 0.68
-
m
-
high pool table, and the ball hits the floor with a speed of 6.0 m/s. How
fast was the ball moving when it left the pool table? (Use the law
of conservation of energy.)

8. A boulder is raised above the ground so that its potential energy relative to the ground is 200 J. Then it is dropped. Wha
t is its kinetic
energy just before it hits the ground?

9. What will be the
kinetic
energy of a
n arrow having a
potential
energy of 50 J after it is shot from a bow?

10
.
What change in kinetic energy does an airplane experience on takeoff if it is moved a distance of 500 m by a sustained net fo
rce of
5000 N?

11
.
A ball is released at the le
ft end of the metal track shown below. Assume it has only enough friction to roll, but not to lessen its
speed.

a
.
Rank from greatest to least the ball’s kinetic energy at each point.

b
.
Rank from greatest to least the ball’s potential energy at e
ach point.

12
. Brittany is changing the tire of her car on a steep hill 20.0 m high. She trips and drops the 10.0
-
kg spare tire, which rolls down the
hill with an initial speed of 2.00 m/s. What is the speed of the tire at the top of the next hill, whi
ch is 5.00 m high?

1
POINT
/
__________

1
POINT
/
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1
POINT
/
__________

3
POINT
S/
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1
POINT
/
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1
POINT
/
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3
POINT
S/
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POINT
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POINT
/
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3
POINT
S/
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5
POINT
S/
__________

3
POINT
S/
__________

13
. A Mexican jumping bean jumps with the aid of a small worm that lives inside the bean. a) If a bean of mass 2.0 g jumps 1.0
cm from
your hand into the air, how much potential energy has it gained in reaching its highest point.

b)

What is its speed as the bean lands back in the palm of your hand?

14
. Relative to the ground below, how many joules of PE does a 1000
-
N boulder have at the top of a 5
-
m ledge? If it falls, with how
much KE will it strike the ground? What will be its
speed on impact?

15
. A can of soup has a mass of 0.35 kg. The can is moved from a shelf that is 1.2 m off the ground to a shelf that is 0.40 m o
ff the
ground. How does the gravitational potential energy of the can change?

True or False, correct it
to make it true if it is false

16
. ___________
The energy an object has by virtue of its location is called its potential energy.

17
. ___________
The energy an object has by virtue of its motion is called its kinetic energy.

18
. Discuss how energy con
servation applies to a pendulum. Where is potential energy the most? The least? Where is kinetic energy
the most? The least? Where is it moving the fastest? Stopped?

1
9. An arrow in a bow has 70 J of potential energy. Assuming no energy loss, how much

kinetic energy will it have after it has been
shot?

20. In what sense is energy from coal actually solar energy? Explain your answer.

21. In what two ways can a machine alter an input force?

22.
In what way is a machine subject to the law of en
ergy conservation? Is it possible for a machine to multiply energy or work input?

23.
What does it mean to say that a machine has a certain mechanical advantage?

24.
In which type of lever is the output force smaller than the input force?

25.

What is t
he efficiency of a machine that
requires 100 J of energy to do 35 J of work?

26
.
Distinguish between theoretical mechanical

How would these compare if a machine

were 100% efficient?

27
.
What is th
e efficiency of her body when a

cyclist expends 1
000 W of power to deliver
mechanical energy to the bicycle at the rate

of
100 W?

28.
What is the t
for each of the three lever systems

shown?

5
POINT
S/
__________

5
POINT
S/
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3
POINT
S/
__________

1
POINT

EACH/
__________

3
POINT
S/
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1
POINT
/
__________

1
POINT
/
_____
_____

1
POINT
/
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1
POINT
/
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1
POINT
/
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1
POINT
/
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1
POINT
/
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1
POINT
/
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1
POINT
/
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3
POINT
S/
__________