Download Second semester final review

Second Semester Review 2014-15
Name
Learning goals are written in italics, questions are in normal font.
Equations at the end of the review
Section 4.2
1. Define energy
What is energy? Explain if it is scalar or vector in nature.
2. Explain what factors affect the speed of a rollercoaster.
Whether a rollercoaster if fully loaded with people or completely empty, the speed at the bottom of the hill is the
same. Explain what factors determine the coaster’s speed at the bottom of the hill?
3. Define and describe kinetic and potential energies.
Identify which of the following has KE, GPE, both, or none.
a. A Car moving on the ground at 15 m/s
b. A fully loaded rollercoaster at the top of a hill moving at 1.0 m/s.
c. A rollercoaster stuck motionless at the top of a clothoid loop.
d. A rollercoaster at the station on the ground picking up new riders.
Write the equations for KE, and GPE and then describe what each of the symbols means (Example: = ;
is the weight of an object.; is the mass of an object; is the acceleration due to gravity)
4. Describe conservation of energy
In your own words, describe the conservation of energy as it relates to a rollercoaster.
5. Identify Joule as unit of energy
Which of the following would be a Joule? ∙ ; 6. Solve problems related to mechanical energy using GPE and KE and energy conservation.
A student measured the speed of a 625 kg roller coaster car at the bottom of this biggest hill at 34 m/s. If the car
started from rest at the top, how high above the ground was the car at the beginning?
7. Apply conservation of energy to everyday events, particularly rollercoasters
Explain why the first hill of rollercoaster is always the tallest hill.
Learning Outcomes for 4.3
8. Define spring potential energy
What is spring potential energy?
What is the equation for spring potential energy?
9. Explain the law of conservation of energy in terms of KE, GPE and SPE and any other type of energy.
During our lab in this section, we studied pop-up toys. Explain the law of conservation of energy in terms of KE,
GPE and SPE for a pop-up toy from when it is sitting stationary on the desk-top to when it reaches its highest point
above the desk-top.
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10. Apply the Law of conservation of energy in terms of KE, GPE, and SPE and any other type of energy.
You start observing a rollercoaster moving at the top of the last hill of its trip. The coaster comes down that last hill,
and then comes into the station and stops. Discuss the energies involved, and apply the conservation of energy to
this portion of the coaster’s trip.
11. Describe thermal friction as energy that is not usable for cases with friction
A roller coaster car is moving on a level track at 25 m/s and has 320,000 J of KE. The emergency brake, which
uses friction to quickly stop the car, is applied and the car comes to a very quick stop. Since the car now has no
KE, offer an explanation that shows what happened to all this energy.
12. Define spring constant, with units
Define spring constant and explain what units are used for a spring constant.
13. Solve problems using Law of Energy Conservation
A toy rocket of mass 0.87 kg uses a spring with a spring constant of 58 N/m, to launch the rocket into the air. If the
spring is compressed a distance of 20.0 cm;
a. What is the SPE before the launch?
b. What would be the KE of the rocket when it leaves the spring?
c. To what maximum height would the rocket go?
14. Analyze energy data to draw conclusions.
Determine the values of the energies in the following data table:
Figure 1 Different Energies for a Pop-Up Toy
at various positions
Position above table
SPE
KE
GPE
(m)
(J)
(J)
(J)
At rest on table
?
0
0
Height = 0
At peak
0
0
100
Height = 0.80
Half way to peak
0
50
?
Height = 0.40
Three quarters to peak
0
?
?
Height = 0.60
TE
(J)
?
?
?
?
Learning goals for 4.4
15. Explain the Universal gravitational law:
Explain what happens to the gravitational force between two objects as the objects get farther apart.
Explain what happens to the gravitational force between two objects as the objects get closer together.
How does the mass of the objects affect the gravitational force of attraction between the two objects?
16. Describe the gravitational field and field lines.
The idea of a gravitational field helps us think of forces that act between two objects that are not in contact. Explain
what the force of gravity would be in a gravitational field if the lines are close together, and if the lines are far apart.
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17. Solve conceptual and mathematical problems on gravitational law.
The gravitational force between two asteroids is 90. Newtons. What would the force be if the distance between the
two asteroids tripled?
The gravitational force between two asteroids is 250. Newtons. What would the force be if one of the asteroids
half of its mass?
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The Mars Curiosity rover has a weight 3,439 N on Mars. If the mass of Mars 6.39 X 10 kg and the distance from
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the surface of Mars to its center is 3.397 x 10 m, determine the mass of Curiosity.
Learning goals for 4.5
18. Distinguish between mass and weight. Calculate weight from mass.
What are at least three differences between mass and weight.
An object has a weight of -750 N. What is the object’s mass?
19. Define Hook’s law and explain why Hooke’s Law has a negative sign.
We saw that the force needed to expand a spring holds a directly linear proportion with the displacement of the
spring. We used this information to write Hooke’s Law as = −, where F is the force applied by the spring, K is
the spring constant and x is the displacement. Explain the reason for including the negative sign on the equation.
20. Solve problems with Hooke’s law.
The suspension in a Formula 1 sports car has a spring with a spring constant of 79,000 N/m. When a 81 kg driver
gets into the car, by how much will the car’s springs compress?
21. Determine the spring constant of a spring through data collection and data analysis (tables and graphs) and
describe a spring based on its spring constant.
The graph below represents the relationship between the force applied to a spring and the stretch (elongation) of
the spring. What is the value of the spring constant?
80
Force (N)
60
40
20
0
0
1
2
distance (m)
3
Data for the
elongation (Displacement) of a spring when the mass of the object
attached is changed
22. Explain similarities and differences between Hooke’s Law and Spring Potential Energy.
Find at least two similarities and two differences between Hooke’s Law and SPE.
23. Define interpolation and extrapolation, and be able to perform them from a graph.
What is the difference between interpolation and extrapolation? Explain by drawing a graph of two variables and
show how you would use interpolation and extrapolation on your graph.
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24. Describe measurement uncertainty from a graph
Assume that the following two graphs were created with data collected during an experiment. Which graph would
you say represents data with the largest uncertainty? Explain your answer.
A)
B)
50
40
40
30
Force 30
(N) 20
Force (N) 20
10
10
0
0
0
5
10
15
0
displacement (m)
5
10
15
Displacement (m)
Figure 5. Force as a function of the displacement for a given spring. Data collected for the same spring by
the A) First group and the B) second group.
Learning goals for 4.6 apparent weight and 4.7 Circular motion
26. Describe the feeling of apparent weight change in an elevator during accelerated and steady motion
A man standing on a bathroom scale in an elevator notices that the scale reads 30 N less than his normal weight.
Describe the possible directions the elevator is moving and the acceleration the man is experiencing.
27. Describe apparent weight through free body diagrams (what causes apparent weight)
Draw a FBD and label the forces on the diagrams for the following three scenerios
a. A person moving up in an elevator at a constant speed.
b. A person moving down in an elevator as the elevator stops.
c. A person moving up in an elevator as the elevator slows down.
28. Perform calculations regarding apparent weight
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Helga is standing on a scale inside an elevator at rest, when the elevator suddenly accelerates up at 2.4 m/s . If
Helga’s mass is 56.0 kg, calculate Helga’s apparent weight during this acceleration?
29. Describe acceleration, and explain the direction of acceleration given a net force and/or change in speed and
direction of motion (speeding up vs. slowing down)
Which of the following scenarios describes an elevator that is accelerating downwards?
Explain your reason for choosing your answer.
a. The elevator is moving down while slowing down.
b. The elevator is moving up while speeding up.
c. The elevator is moving down at constant speed.
d. The elevator is moving up while slowing down.
Circular motion
30. Define and describe centripetal force
Define centripetal force and include the direction in which it points relative to the motion
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31. Define and describe centripetal acceleration
Define centripetal acceleration
Describe the difference between centripetal acceleration and centripetal force
32. Solve problems with centripetal force
Calculate the centripetal force acting on a cart that has 3500 kg of mass, as it travels at 8 m/s in a loop with a
radius of 18 m.
33. Describe acceleration in terms of g
How many g’s of centripetal acceleration would a person experience in a ride whose acceleration is recorded to be
33 ?
34. Apply centripetal force and centripetal acceleration to the design of a rollercoaster
Calculate the radius of the upper curve of a clothoidal loop given that the designer wants it to have 3.5 g of
centripetal acceleration for a cart with 3850 kg and a speed of 15 m/s.
Calculate the centripetal force that a 75 kg person would experience in the same ride
35. Apply centripetal force and acceleration to apparent weight. Apparent weight is the normal force for a rider, what
we have been calling Force by the sensor or scale.
Determine the apparent weight that a scale would read for a person with a mass of 65 kg on a rollercoaster that
experiences 3.0 g’s of centripetal acceleration.
36. Draw free-body of an object (person, roller coaster car) moving in a circular motion.
Suppose a person on a roller coaster is sitting on a scale as the roller coaster moves along a track. Draw the freebody diagram of the person when the person in at the bottom of a vertical loop and when the person is at the very
top of a vertical loop.
37. Explain the importance of a clothoid loop in roller coaster design.
Explain the need for clothoid loops in vertical loops of rollercoaster, as well as why horizontal loops require no
clothoid loops. Please use the following words: Velocity, kinetic energy, gravitational potential energy, centripetal
acceleration, radius.
Work and power
38. Describe and define work
Define the word “work” as it is used in physics
39. Know the units and symbol for work, and express them in terms of basic units
Write the unit of work in terms of the basic units: kg, s, m
Which of the following are units of work (more than one answer): N, J, W (as in Watt), Nm, J/s, Watt times second
40. Differentiate between work and force
Describe a scenario in which a person displaces the very same object two separate times on the same planet with
the exact same force, but does different amount of work.
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41. Differentiate between distance and displacement
Describe a scenario in which Lulu travels twice as much distance as Jennie, but ends up with a displacement that
is half of Jennie’s displacement.
42. Explain the relationship between work and gravitational potential energy and spring potential energy
Explain how you could calculate the work done on a 2500 kg cart that is lifted along an inclined track to a height of
45 m if you do not know the force along the track and do not know the distance along the track either.
43. Break down, or resolve, the force into component parallel to the displacement using trigonometric functions.
A rollercoaster cart is raised 33 m on a track that is at 25° from the horizontal. A force of 25000N is applied along
the track. (Think about the direction of the displacement and the components of the force for this one).
A.)Calculate the work done on the cart.
B) Calculate the gravitational potential energy gained by the cart as it reached the new height.
44. Describe and define power
Define power and write its equation.
45. Know the units and symbol for power, and express them in terms of basic units
Write the unit of power in terms of the basic units: kg, s, m
Which of the following are units of power (more than one answer): N, J, W (as in Watt), Nm, J/s, Watt times
second, Newton time meter divided by second square.
46. Solve problems with work and power
Calculate the power done on a vacuum cleaner pulled 3.0 m in 2.0 seconds with a force of 50.0 N at an angle of
30.0° above the horizontal.
Momentum
47. Define momentum
Write the equation that allows you to calculate the momentum of an object in motion.
48. Solve problems involving momentum
How much momentum would a 450 kg bumper car have at the fair when traveling at 6.0m/s
49. Describe conservation of momentum
Describe what we mean by the words conservation of momentum
Write the equation that describes conservation of momentum.
50. Solve problems with conservation of momentum
Calculate the final momentum that a red bumper car would have after a collision with a blue bumper car given that:
the blue car has 345 kg of mass, was moving at 7.0m/s before the collision and ended up moving at -3.5m/s after
the collision. The red car began moving at -5.4m/s and has a mass of 405 kg.
A police officer shows up to a crash scene in which car A, with a mass of 4500kg crashed with car B, with 5300 kg.
She is able to reconstruct the accident and determines that car A was traveling at 35m/s before the accident and
car B was traveling at -23m/s. Calculate the final velocity of car B, if the car A ended up moving at 7.9m/s.
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51. Use momentum to describe everyday phenomena
Explain why a basketball ends up bouncing at the same speed but opposite direction from the floor using the idea
of momentum.
Learning goals for 5.1 and 5.2 Sound
52. Explain what pitch is.
Define pitch.
53. Describe the relationship between tension and length of string with the pitch of a vibrating string
Explain how two strings of different lengths can produce the same pitch.
Two strings of different lengths produce different pitches. Explain how this is possible.
54. Define a wave
Provide the definition of a wave seen in class.
Explain why moving your hand back and forth in a “wave” is not a physics wave
55. Indicate requirement for mechanical waves
Write a recipe for creating a mechanical wave. Your recipe must include the basic two ingredients for mechanical
waves.
56. Describe the difference between periodic and pulse waves
Modify your recipe from the previous question to create a periodic wave and a pulse wave.
57. Identify parts of a wave: amplitude, wave length, crest, trough, period, frequency
In the following diagrams, identify and label which is longitudinal and transverse, and identify and label the
wavelength for both. Also label the crest and trough for the appropriate wave.
In the first wave above, identify and label the amplitude, and two crests and two troughs.
Determine the frequency in Hertz (Hz) for a wave given that 24 waves were counted in 60 seconds. Determine the
wave’s period as well.
58. Define wave speed, amplitude
Calculate the speed of a wave with amplitude of 20 cm that travels 305 cm in 0.67s
Describe the relationship between amplitude and wave speed
59. Describe the relationship between amplitude and energy of a wave
Describe what determines the energy of a mechanical wave
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60. Define and calculate the frequency, period, wavelength and speed of a wave
Explain how period and frequency are related
A particular wave on a slinky has a period of 0.5s, what is the frequency of this wave?
A surface water wave is traveling at 5.0 m/s, and has a wavelength of 10 m. Determine the frequency and period of
this wave.
The distance the crest of a wave moves in 0.5 s is 4.5 m. Calculate the wave speed.
61. Explain what happens when two waves interact with each other (wave interference)
Draw a diagram to illustrate constructive interference
Draw a diagram to illustrate destructive interference
62. Describe the process for forming standing waves
Explain why you need to continue to move you hand back and forth while holding the slinky to produce a standing
wave, while your partner keeps the other side of the slinky motionless
63. Draw a standing wave and label the nodes and antinodes
Explain why the following diagram does not correspond to a standing wave
Sketch a standing wave with two and a half wavelengths. Identify the nodes and the
antinodes
For a certain standing wave, the distance between two nodesis known to be 0.32 m. What is the wavelength of this
standing wave?
64. Know the units related to waves
Write the symbol for the following units:
a.
b.
c.
d.
e.
f.
g.
m/s
m
s
1/s
Hz
cm
cm/s
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Equations for Physics Second Semester Exam
Equations seen during second semester, in the order in which we saw them in class.
You may remove this sheet so you can see it at all times.
=
+ − ∆ − ∆
=
= =
=
= ∆
− 2
∆
− 1
1
= ! = ℎ#! = $ %& = %
2
2
' = '
=
(
) *
1 = 1000
1 = 1003
456 = 2 + 0
8 = ∥ = = = 6.6710/&&
7 =
0
12
1 = 1000
*
∥ = 3:;Θ
=>5?*5 = =@65*
7 =
!=
*
6
' = −9.81 1
= CDC = %
9
= −$