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Name_________________________ Due Date__________
Physics Ib
Topic 05b – Energy
HW #1: ____/5
HW #2: ____/5
Performance Packet
SCORE______/90
For Full Credit:
1. SHOW WORK: Each answer must be accompanied by work or reasoning. For math questions you
should show the original equation you used and then show the substitutions you made (with units!). All nonmath responses should be in complete sentences.
2. WORK IN PENCIL and BOX your final answers.
Healthy Collaboration:
You collaborate to do better work, not less work. You must answer every question yourself.
Collaboration is for discussing process (how to get started on a problem) and for checking answers. You are
crossing the line into copying if you write something down simply because 1) you saw it on another’s paper, 2)
you read it from another’s calculator, or 3) you heard someone else say it.
Section #0 Review Questions (20 points)
1.2 – Measurement and Units
1) Convert 9.8
meters
into feet/second2.
2
second
1.5 – Scalar and Vector Quantities
2) What is the vector sum of 20 m north and 48 m west? Give magnitude and
approximate direction.
2.2 – Graphs of Constant Velocity
3) The motion of a raging yak is shown to the
right. What is the total distance the yak
travels in five seconds?
30
velocity (m/s)
20
10
0
-10
-20
1
2
3
4
5
6
time (s)
3.3 – Model of Constant
Acceleration
4) & 6) A car accelerates from 30
m/s to 5 m/s in 10 seconds. Fill
in the chart; show your work.
Energy - Performance
vi
vf
Page 1 of 12
v̅
Δv
a
Δt
Topic 05b
Δs
3.2 – Graphs & Maps of Constant
Acceleration
5) The graph (right) shows the motion of a
wombat. Fill in all of the blocks of the
motion chart by using the graph
5
4
Velocity (m/s)
3
2
1
0
1
vi
vf
v̅
Δv
a
Δt
2
Δs
3
4
5
6
time (s)
4.2 – Force Vectors
7) Draw a free body diagram for a book pressed horizontally into a wall.
4.3 – Gravitational Forces
8) Cyrus has a mass of 75 kg on earth. What are his mass and weight on Mars?
4.4 – Interactions with Surfaces
9) A box of mass 12 kg is pulled along at a constant velocity by a force of 30 N. What is
the coefficient of friction between the box and the floor?
4.5 – Tension
10) A 60 kg box is hung from two vertical ropes. What is the tension in each rope?
Energy - Performance
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Topic 05b
Section #1 Easy Questions (1 point each)
5.1 - Energy: Intro & Flavors
1) What flavor(s) of energy does a bowling ball rolling down an alley have?
2) A skydiver is hovering in a helicopter about to jump. What flavor(s) of energy does she
have?
3) A blacksmith pulls a bar of red-hot iron out of a forge. What flavor(s) of energy does
the bar have?
4) A bungee jumper is hanging motionless from a bungee cord, halfway between a bridge
and the river below. What flavor(s) of energy do the jumper and bungee cord together
have?
5.2 - Transferring Energy
5) A crate is pushed by a 200 N force over a distance of 1.7 m. How much energy is
transferred to it?
6) A landing airplane has 100,000 J of kinetic energy. How much work will have to be done
on the airplane to bring it to a stop?
7) A certain bucket of water has 2000 J of thermal energy. Express this amount in
standard units.
5.3 - Power
8) What is the power of a light bulb that uses 60 Joules of energy every second?
9) How powerful does a tow truck have to be to pull a car with a force of 10,000 N for a
distance of 100 m in 12 seconds?
5.4 - Work Causes Change
10) A 25 kg skateboarder is riding along at 3 m/s. How much kinetic energy does he have?
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Topic 05b
11) An 80 kg sky diver is sitting at the door of an airplane 850 m above the ground. What
is her gravitational potential energy relative to the ground?
12) A 1000 kg car is driving at 10 m/s. If it doubles its speed, its kinetic energy is…
A. quadrupled
B. doubled
C. stays same
D. cut in half
E. cut in quarter
13) A box at rest is pushed by a 20 N force for 10 m across a frictionless sheet of ice.
How much kinetic energy does it end up with?
5.5 - Springs
14) How much force does it take to stretch a spring (k=100N/m) by 0.15 m?
15) What is the elastic constant of a spring that requires 30 N of force to stretch by 10
cm?
16) How much energy is stored in a spring with a elastic constant of 700 N/m stretched
out by 0.2 m?
5.6 – Conservation of Energy
17) A hammer with 100 J of potential energy is dropped to the floor. How much kinetic
energy does the hammer have just before it hits the ground?
18) A couch sliding across a flat floor with 1200 Joules of kinetic energy slides to a stop.
What flavor is most of the energy once the couch stops sliding?
19) A ball has 45 J of gravitational potential energy when it is first dropped from rest, but
40 J of gravitational potential energy at the top of its first bounce. How much energy
did the ball “lose”?
20) What is the new “flavor” of the missing energy in question 19?
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Topic 05b
Section #2 Moderate Questions (2 point each)
5.1 - Energy: Intro & Flavors
1) At the top of a cliff, all of a base jumper’s energy is gravitational potential energy.
Halfway down, what percentage is now kinetic energy?
5.2 - Transferring Energy
2) How much work is required to raise a 17 kg gold bar up two meters?
5.3 - Power
3) A certain motor can put out 7500 J in ten minutes. What is its power rating?
4) How much work can a 250 Watt motor do in a minute?
5.4 - Work Causes Change
5) A 1400 kg car accelerates from 12 m/s to 24 m/s. How much kinetic energy does it
gain?
6) What is the velocity of a 0.48 kg pinewood derby car that has a kinetic energy of 2.16
J?
7) How much work is required to raise a 60 kg crate up 5.7 meters?
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Topic 05b
100
5.5 – Springs
8) Data collected on a spring are graphed to
the right. What is the elastic constant of
this spring?
Force (N)
80
60
40
20
0
0.1
0.2
0.3
0.4
0.5
0.6
displacement (m)
5.6 – Conservation of Energy
9) A 0.85 kg ball is thrown upward at 40 m/s. Later, it is still moving up at a height of 60
m above the ground. Conserve energy to find out how fast it is going at this point.
system: ball and earth
KE
PEg
PEel
Thermal
KE
PEg
PEel
Thermal
10) A cart comes crashing into a spring, as shown in the diagram. At the instant the cart
comes to a stop, by how much is the spring compressed? Conserve energy to answer
the question.
system:
KE
Energy - Performance
PEg
PEel
Page 6 of 12
Thermal
KE
PEg
PEel
Topic 05b
Thermal
250
Section #3 Hard Questions
5.2 - Transferring Energy
1) (3 points) A stationary baseball is hit by a
bat. The force and displacement are shown
on the graph. How much kinetic energy does
the ball end up with?
Force (N)
200
150
100
50
0
0.1
0.2
0.3
0.4
0.5
0.6
displacement (m)
5.5 – Springs
2) (3 points) A certain spring has a elastic
constant of 200 N/m. Graph the force vs.
displacement for this spring. Show on the
graph the amount of energy added to the
spring when it is stretched from 15 cm to 25
cm. Calculate how much energy this is.
250
Force (N)
200
150
100
50
0
0.5
1.0
1.5
2.0
2.5
3.0
displacement (m)
5.6 – Conservation of Energy
3) (4 points) The bullet strikes a block of wood which exerts, on average, a force of
50,000N opposing the motion of the bullet. How far does the bullet penetrate?
(HINT: system=bullet)
Initial
Final
KE
Energy - Performance
PEg
PEel
Thermal
Page 7 of 12
KE
PEg
PEel
Thermal
Topic 05b
Section #4 Short Answer Questions (2 points each)
5.1 - Energy: Intro & Flavors
1) Another flavor of energy is nuclear energy. This flavor is associated with the
arrangement of protons and neutrons in the nucleus of an atom; it is used in nuclear
power plants. Is this flavor an energy of motion or an energy of position? Explain your
answer.
5.2 - Transferring Energy
2) Give two examples where a force is pushing on an object, but it is not doing any work.
5.4 - Work Causes Change
3) Does every stationary object contain potential energy? Explain.
5.5 - Springs
4) Compare the elastic constants of a stiff spring and a “floppy” spring.
5.6 – Conservation of Energy
5) If you slide across the dirt (baseball, maybe?), you start out with kinetic energy.
Where does all this energy go? List flavors, and explain.
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Topic 05b
Section #5 Project Question: ALGEBRA (10 points)
5.4 - Work Causes Change
5.6 – Conservation of Energy
A 38 kg box is tipped off a 64 m high cliff. For each
of the four locations marked (top of cliff, one-quarter
down, halfway down, just above the ground), find the
kinetic and gravitational potential energy of the box.
In addition, find the speed of the box at each location!
Show your work clearly for each position:
TOP OF CLIFF:
___________
speed at top:
top of
cliff
one-quarter
down
halfway
down
ONE-QUARTER DOWN:
speed at ¼: ___________
HALFWAY DOWN:
speed at ½: ___________
JUST ABOVE GROUND:
Energy - Performance
just above
ground
speed just above ground: ___________
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Topic 05b
Section #6 Project Question: GEOMETRY & VECTORS (10 points)
5.3 - Power
1) A motor lifts a load by winding up a rope on a drum (see
diagram). The motor rotates the drum. The drum has a
radius of 0.5 m.
Rotating
Drum
a) What is the circumference of the drum?
b) When the drum fully rotates once, by how much
distance is the load lifted up?
Load
c) The drum rotates three times in one second. What is the speed of the drum’s
rotation?
d) The maximum load that the motor can lift in this way is 74.5 kg. What is the
weight of this load?
e) What is the Power of the motor, in Watts?
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Topic 05b
Force (N)
Section #7 Project Question: GRAPHING (10 points)
5.2 - Transferring Energy
1500
5.4 – Work Causes Change
BOBSLEDDING:
1200
Bobsled races start with a
50m long “push”, during
900
which the riders push on
600
the sled to get it moving as
fast as possible. A typical
300
4-person bobsled has a mass
of 630 kg.
0
10
20
30
40
Displacement (m)
1) 5.2 (4 points) How much
energy do the pushers transfer to the bobsled during the push graphed above?
2) 5.2 (3 points) Approximately 2/3 of the energy transferred to the sled takes the form
of kinetic energy. The remaining 1/3 of the energy becomes thermal energy in the sled
and in the snow. How much kinetic energy will the sled have at the end of its push?
3) 5.4 (3 points) What is the final velocity of the bobsled at the end of this push?
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Topic 05b
50
Section #8 Project Question: MODELS (10 points)
5.5 – Springs
36.0
5.6 – Conservation of Energy
Data were collected on two springs;
Data Set 1
32.0
Data Set 2
these are graphed on the right.
1) 5.5 (2 pts) Determine the spring
constant for spring 1.
28.0
24.0
Force (N)
20.0
16.0
2) 5.5 (2 pts) Determine the spring
constant for spring 2.
12.0
8.00
4.00
0.00
0.00
2.00
3) 5.5 (2 pts) Compare the amount
of force required to stretch each spring by 3 meters.
4.00
∆s (m)
6.00
8.00
4) 5.5 (2 pts) Determine the energy stored by spring 1 when it is stretched by 3 m.
5) 5.6 (2 pts) Spring #2 is compressed by 3m and used to shoot a 0.05 kg rock straight
upward. How much potential energy will the rock have at the top of its flight?
Energy - Performance
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Topic 05b