Exam 3 information Exam 3 will be held Monday, 11/24 at 7:30 pm in TBA. The exam is design to take one hour and you will be given 75 minutes to complete your work. The Exam will cover material in chapters 8-11. Some practice exam problems are available on the class web site. You will not need a scantron. The exam book and formula sheet will be provided to you. You will need your TAMU ID and remember your section number and lecturers name. You will be allowed to use a calculator (simple), but if you have a programmable calculator, you must have cleared its memory BEFORE coming to the exam. Cell phones should be turned off and stored for the exam period. Any use of cell phones during the exam is prohibited and if used will be considered an Honor Code violation. 11/25/2014 Physics 218 1
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Exam 3 information Exam 3 will be held Monday, 11/24 at 7:30 pm in TBA.
The exam is design to take one hour and you will be given 75 minutes to complete your work. The Exam will cover material in chapters 8-11.
Some practice exam problems are available on the class web site.
You will not need a scantron. The exam book and formula sheet will be provided to you.
You will need your TAMU ID and remember your section number and lecturers name.
You will be allowed to use a calculator (simple), but if you have a programmable calculator, you must have cleared its memory BEFORE coming to the exam.
Cell phones should be turned off and stored for the exam period. Any use of cell phones during the exam is prohibited and if used will be considered an Honor Code violation.
11/25/2014 Physics 218 1
Chapter 13
Gravitation
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Learning Goals
How to calculate the gravitational forces that two bodies exert on each other.
How to relate the weight of an object to the general expression for gravitational force.
How to use and interpret the generalized expression for gravitational potential energy.
How to relate the speed, orbital period, and mechanical energy of a satellite in circular orbit.
The laws that describe the motions of the planets and how to work with these laws (Kepler’s Laws)
11/25/2014 Physics 218 3
Kepler’s Laws
Each Planet moves in an elliptical orbit with the sun at one focus of the ellipse.
A line from the sun to a given planet sweeps out equal areas in equal times.
The periods of the planets are proportional to the 3/2 power of the major axis lengths of their orbits.
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Figure 13.18
The First Law
Figure 13.19
Kepler’s Second Law
m
Lvrrv
dt
dr
dt
dA
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21
2
21
Kepler’s Third Law
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aT
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2
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Calculation the period for our Moon’s Orbit
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dsX
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8
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Radius of the Earth’s orbit
11/25/2014 Physics 218 9
mXr
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S
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32
32
Geosynchronous Satellites
Period of the orbit =
same as the orbital rotation of the earth
Satellite will the appear to stay fixed in the sky above a point on the earth.
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11/25/2014 Physics 218 11
earth theofcenter thefrom miles 1059.2
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Chapter 14
Periodic Motion
Goals for Chapter 14
• To describe oscillations in terms of amplitude, period, frequency and angular frequency
• To do calculations with simple harmonic motion
• To analyze simple harmonic motion using energy
• To apply the ideas of simple harmonic motion to different physical situations
• To analyze the motion of a simple pendulum
• To examine the characteristics of a physical pendulum
• To explore how oscillations die out
• To learn how a driving force can cause resonance
Introduction
• Why do dogs walk faster than humans? Does it have
anything to do with the characteristics of their legs?
• Many kinds of motion (such as a pendulum, musical
vibrations, and pistons in car engines) repeat themselves.
We call such behavior periodic motion or oscillation.
What causes periodic motion?
• If a body attached to a spring is displaced from its equilibrium position, the spring exerts a restoring force on it, which tends to restore the object to the equilibrium position. This force causes oscillation of the system, or periodic motion.
• Figure 14.2 at the right illustrates the restoring force Fx.
Characteristics of periodic motion
• The amplitude, A, is the maximum magnitude of displacement from equilibrium.
• The period, T, is the time for one cycle.
• The frequency, f, is the number of cycles per unit time.
• The angular frequency, , is 2π times the frequency: = 2πf.
• The frequency and period are reciprocals of each other: f = 1/T and T = 1/f.
Simple harmonic motion (SHM)
• When the restoring force is directly proportional to the displacement from equilibrium, the resulting motion is called simple harmonic motion (SHM).
• An ideal spring obeys Hooke’s law, so the restoring force is Fx = –kx, which