Download UNIT VII ENERGY: WS 1 Qualitative Analysis

Freshman Physics - Semester 1 Review
Name______________________________
The intent of this packet is to provide prompts and problems to remind you of some of the topics we’ve
touched on so far this semester. The final exam may include but is not exclusive to the enclosed information.
Energy
LAW OF CONSERVATION OF ENERGY – energy can not be created nor destroyed
Energy Storage Mechanisms
E kinetic – E stored as motion
E Elastic - E stored in the distortion (stretching, bending, twisting, pressing) of an object that will return to
its original shape
E Gravitational – E stored in position (vertical)
E Chemical – E stored in chemical bonds (can be released when we burn sugar (food) or gasoline)
E Internal (dissipated) - A catch all phrase for energy that is stored as light, sound, or an increase in
temperature due to friction
Give an example of how each of these could be increased/decreased
Energy Transfer Mechanisms
Radiating- E entering/exiting a system via electromagnetic waves
Working - E entering/exiting a system by something being physically moved by an external force
Heating - E entering/exiting a system because of a difference in temperature
Which E storage mechanism is most closely related to the following prompts




Energy stored in motion
Energy stored in chemical bonds (can be released when we burn sugar or gasoline)
Energy stored in the vertical position of an object
Energy stored in the distortion (stretching, bending, twisting, pressing) of an object that will return to its
original shape

A “catch all phrase” for energy that is stored as light, sound, or an increase in temperature due to friction

The faster an object goes, the more __________ it has

A clock or toy that has been wound has a lot of this.

As a ball rolls down a hill it has less of this.

The noise we heard when the meter stick smacked into the table is an example of this way of storing energy.

You have more of this after you eat.
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Use pie charts to analyze the energy changes in each situation given.
•
•
•
•
Designate your choice of system with a dotted line Choose your system so that the energies involved are internal (within the
system).
Carefully label the pies to correspond with the positions of the objects given. (A, B, C, etc.)
The pies should be accurately divided and labeled with the energy storage mechanisms involved.
Remember the 4 energy questions in deciding about the energy changes:
1. What is the system?
2. How is the energy stored?
3. Is energy transferred in or out of the system?
4. How is the system changing?
1. A wind-up toy is wound up, then "walks" across a table and comes to a stop.
2. A pendulum is held up to your nose. When it is released, it swings away from your nose and then
returns.
3. A squeeze flashlight is held in your hand. You squeeze the handle hard so that it lights. Include
yourself in the system.
4. You press your palms together and then rub your palms up and down against each other. Include
yourself in the system.
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4. A Cheeto is set on fire with a lighter. The lighter is turned off while the Cheeto continues to burn
itself out.
5. A ball is held above the ground, and then is dropped
so it falls straight down. (Restrict your analysis to
the ball being in the air, BEFORE it hits the ground.)
7. A baseball is thrown up in the air and then falls back down. Place velocity vectors
each corresponding baseball in the drawing, and
do a pie for each position.
beside
8. A wind-up Volkswagen has been wound up and set on a tabletop. As the spring unwinds, it speeds
up. When it is fully unwound, it slows to a stop.
British and Metric (and more) Units Conversions Review
Equivalents:
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Length: 12 in. = 1 ft.
3 ft. = 1 yd.
Time: 60 s = 1 min. 60 min = 1 hr
24 hr = 1day
Weight: 16 oz. = 1 lb.
2,000 lb. = 1 ton
k
h
d
m
d
c
m
length:
km hm dkm m
dm cm mm
mass:
kg
hg
dkg g
dg
cg
mg
capacity:
kL hL dkL L
dL cL
mL
1760 yd. = 1 mi.
365 days = 1 yr
2.54 cm = 1 in.
Show your work. Include Units. Please box answers with units.
a.
3.1 mi ft
b.
2 day  s
c.
128 lb.  oz.
d.
4323 in  yd
e.
42.5 m  km
f. 7cm/s  m/s
g. 3ft  m
h.
20 m/s  mi./hr.
i. Aliens landed and took over the world and rationed our water. You want 1800 “drags” of water. How
many gallons would you have to ask for IF:
15marps = 1 turp
10 turps = 1 drag
6 drags = 1 pak
2 pak = 1 gallons
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UNIT I: Constant Velocity Review
1.
Consider the position vs. time graph below for cyclists A and B.
a.
b.
c.
d.
e.
Do the cyclists start at the same point? How do you know? If not, which is ahead?
At t= 7s, which cyclist is ahead? How do you know?
Which cyclist is travelling faster at t = 3s? How do you know?
Are their velocities equal at any time? How do you know?
What is happening at the intersection of lines A and B?
2.
Consider the position vs time graph at right.
a. Determine the average velocity of the object.
b. Write a mathematical equation to describe the
motion of the object.
3.
Shown at right is a velocity vs time graph
for an object.
a. Describe the motion of the object.
b. How far did the object travel in the interval t =1s
to t =2s?
c. What is the total displacement? Explain how you
got the answer.
d. Draw the corresponding position vs time graph.
Number the x - axis
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4. Johnny drives to Wisconsin (1920 miles) in 32 hours. He returns home by the same route in
the same amount of time.
a.
Determine his average speed.
5.
b.
Determine his average velocity.
c.
Compare these two values and explain any differences.
Consider the v vs t graph below.
a. Describe the behavior of the object depicted in the graph.
b. Draw a motion map that represents the behavior of the object.
6. A race car travels at a speed of 95 m/s. How far does it travel in 12.5 s? Use the
appropriate mathematical model and show how units.
8. a. Find the slope with units.
b. What is the meaning of the slope with units?
c. What is the physical significance of the slope?
d. What is the mathematical model of the line?
e. What is the position at 2s, 3s, 17s?
f. What is the velocity at 5s?
g. Build a velocity vs. time graph for 5s. Scale the axis.
h. Find the displacement for 0-5s.
i. What would the velocity be if the time were doubled?
j. What would the displacement be if the time were
P
o
si
ti
o
n
20
(m)
3
Time(s)
v
doubled?
time
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Unit II: Uniform Acceleration Review
Slowing down, moving in the positive direction
a. Observe the motion of the cart slowing after an initial push without using the motion detector.
Answer the following questions for the cart while coasting.
Stop the cart at
its highest point.
Give the cart an initial push up the ramp.
cart
1. Draw a motion map including both velocity and acceleration vectors.
+
0
2. Is the velocity positive or negative?
3. Is the acceleration positive or negative?
position
4.+Record the graphs as displayed by the motion detector.
5.
6.
7.
0
+
8.
velocity
t
9.
0
t
10.
11.
acceleration
+
12.
0
t
13.
g. (5-13) On the observed graphs, describe the slope as
a) constant, increasing or decreasing
b) positive, negative, or zero
c) state what the slope represents
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1. The data to the left are for a wheel rolling from rest down an incline. Using the position/time data given
in the data table, plot the position vs. time graph.
x
t
1. (s)2. (cm)
0.0
0.0
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1.0
2
2.0
8
3.0
18
4.0
32
5.0
50
6.0
72
2. What is the significance of the slope of a position vs. time graph?
3. What is happening to the slope of your position vs. time graph as time goes on?
4. On the position vs. time graph, draw a line which connects the point at t = 0 to the point at t = 6.0 s.
5. Calculate the slope of this line in the space below. Explain what the slope of this line tells you about the
motion of the wheel. Write your explanation in the space to the right of your slope calculation.
6. On the position vs. time graph, draw a line tangent to the graph at t = 3.0 s.
7. Calculate the slope of this line in the space below. Explain what the slope of this line tells you about the
motion of the wheel. Write your explanation in the space to the right of your slope calculation.
8. Compare the slopes you have calculated in questions 5 and 7. Explain the results of your comparison.
9. Consider an object accelerates uniformly. If you were to calculate the average speed of the object for a
given interval of time, would the object ever be traveling with an instantaneous speed equal to that average
speed? If so when? Explain!
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10. Use the position vs. time data to complete the data table to the right. Using the completed table, plaot a
velocity vs. time graph on the axes below. Perform a mathematical analysis of the resulting velocity vs. time
graph in the space provided, to yield a mathematical model that describes the relationship between velocity
and time for this wheel.
t mid
Mathematical Analysis:
x
x
t
v
t
2. (s)3. (cm) (s)
(cm)
(s) (cm/s)
0.0
0.0
4.
5.
6.
7.
8.
9.
10.
11.
1.0
12.2
13.
14.
15.
16.
17.
18.
19.
2.0
20.8
21.
22.
23.
24.
25.
26.
27.
3.0
28.
18
29.
30.
31.
32.
33.
34.
35.
4.0
36.
32
37.
38.
39.
40.
41.
42.
43.
5.0
44.
50
45.
46.
47.
48.
49.
50.
51.
6.0
52.
72
53.
54.
55.
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11. Based on the shape of your position vs. time
graph for these data, it should be clear to you that
further manipulation of the data is necessary in
order to develop a mathematical model that
describes the relationship between position and
time. Complete the data table to the right and
plot a graph of position vs. time2. Why were you
asked to square time and make this new plot? In
the space provided, perform the mathematical
analysis of the position vs. time2 graph to
develop the mathematical model that describes
the relationship between position and time.
t
x
(s)
(cm)
0.0
0.0
1.0
2
2.0
8
3.0
18
4.0
32
5.0
50
6.0
72
Mathematical Analysis:
t2
(s2)
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12.
What is the significance of the slope of your velocity vs. time graph? Explain!
13. Compare the slope of your velocity vs. time graph to the slope of your position vs. time2 graph. What does
this say about the significance of the slope of your position vs. time2 graph.
14. Write the equation which relates velocity and time for the wheel using the mathematical analysis of your
velocity vs. time graph.
15. Write the equation which relates position and time for the wheel using the mathematical analysis of your
position vs. time2 graph.
16. What does the area under a velocity vs. time graph tell you?
17. What would be the object’s velocity at 15s? Show all work.
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Type of Motion and Direction of Acceleration.
SU + dir
SU – dir
SD + dir
SD - dir
t
0
position
position
t
0
0
velocity
t
0
t
t
+
+
t
t
+
+
+
t
0
velocity
0
+
4.
0
acceleratio
n
acceleratio
n
velocity
velocity
t
+
0
0
+
+
0
3
position
t
acceleratio
n
0
+
2.+
acceleratio
n
1.
position
+
0
t
t
5. Build a motion map below each stack.
When speeding up (SU), the acceleration is always in the same direction as the motion.
When slowing down (SD), the acceleration is always in the opposite direction of the motion.
6. If a ball was rolling down a ramp, v0= 0 m/s and a =2 m/s2
a. What would the velocity be at 5 s?
V(m/s)
b. What would the velocity be at 10 s?
2
c. What happens to the velocity if you double the time elapsed?
2
d. What would the displacement be at 5s? (Use a graphical representation)
e. What would the displacement be at 10s? (Use a mathematical rep)
f. What happens to the displacement if you double the time elapsed?
g. What would the velocity be at 23 s
h. What would the displacement be at 23s(Use a mathematical representation)
i. What would be the displacement from 5s-6s?
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4
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Use the graph below to answer questions #1-4 that follow:
1. Give a written description to describe the motion of this object.
2. Draw the motion map for the object. Include velocity and acceleration vectors.
3. Explain how you could determine the instantaneous velocity of the object at t = 2 s.
4. Assume the initial velocity was 50 m/s; determine the acceleration of the object.
5.
A Pontiac Trans-Am, initially at rest, accelerates at a constant rate of 4.0 m/s2 for 6 s. How fast will
the car be traveling at t = 6 s?
6. A wheel and axle rolls in a positive directions down the ramp, uniformly accelerating, from rest.
a. If its velocity is 6cm/s at t = 2s, what is the acceleration?
b. Based on that acceleration, what would the velocity be at 4s?
c. Based on that acceleration, what would the velocity be at 8s?
d. If we doubled the rate of acceleration, what would the velocity be at 4s?
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7. For each of the position vs time graphs shown below, draw the corresponding
v vs t, a vs t , and motion map.
8.
Using the graph below, compare the kinematic behavior of the two objects.
Comparison:
is A > B, A < B, or A = B,
a. Displacement at 3 s
b. Average velocity from 0 - 3 s
c. Instantaneous velocity at 3 s
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How do you know?
Forces Review.
Consider the puck below at rest on a level air table.
1. The air table is turned on
a. Draw a force diagram for the puck
b. Is the puck accelerating?
c. What is the ∑F?
d. Describe the motion of the puck.
e. Draw a motion map for the puck.
2. The puck receives a constant push of air to the right.
a. Draw a force diagram for the puck
b. Is the puck accelerating?
c. What is the ∑F?
d. Describe the motion of the puck.
e. Draw a motion map for the puck.
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3. The blower is turned off.
a. Draw a force diagram for the puck
b. Is the puck accelerating?
c. What is the ∑F?
d. Describe the motion of the puck.
e. Draw a motion map for the puck.
4. The is air table is turned off.
a. Draw a force diagram for the puck
b. Is the puck accelerating?
c. What is the ∑F?
d. Describe the motion of the puck.
e. Draw a motion map for the puck.
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You may assume: ge = 10N/kg
gm = 1.6N/kg
1. An object has a mass of 16kg. What is the force due to gravity (weight of) on the object?
7. An object has a mass of 50kg. What is the force due to gravity (weight of) on the object?
8. An object has a mass of 500g. What is the force due to gravity (weight of) on the object?
9. Gravity exerts a force of 480N on an object. What is the mass of the object?
10. An object “A” on the earth weighs 14N. A second object “B” weighs 14N on the moon. Assuming
the gm = 1.6N/kg on the moon, which object has more mass? Show your work.
11. A rock weighs 20N on the earth, what is its mass on the moon?
12. An astronaut’s tool kit has a mass of 8kg on the Moon. What’s its mass on the Earth?
14. An object that weighs 168N on the Earth is taken to Triton and weighs 12N. What is the g on Triton?
Uniform Motion formulae Area Formulae
x
t
v f  v i  at
x
v T
tT
d
v T
tT
v






Area Formulae
Rectangle
A  bh
Triangle
1
A  bh
2
Trapezoid
1
A  (b1  b2 )h
2
Uniform Acceleration Formulae

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v
t
1
x  at 2  v it
2
v f  v i  at
1
x  (v i  v f )t
2
a




x  x f  x 0
x
t
x  v t  x0
v
x  v t
v
t
v  v 0  at
a
v  at
2
x  x0  v0 t  1 2 at
x  v0 t  1 2 at 2
v 2  v 20  2ax
FG = g * m
2
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