Hillcrest Science Investigations

Physical Science HW # 3

Physics
The law of conservation of energy provides one of the basic keys to understanding the universe. The fundamental
tenet of this law is that the total mass-energy of the universe is constant; however, energy can be transferred in
many ways. Historically, scientists have treated the law of conservation of matter and energy separately. All energy
can be classified as either kinetic or potential. When work is done on or by a system, the energy of the system
changes. This relationship is known as the work-energy theorem.
Energy may be transferred by matter or by waves. Waves transfer energy without transferring mass. Most of the
information scientists gather about the universe is derived by detecting and analyzing waves. This process has been
enhanced through the use of digital analysis. Types of waves include mechanical and electromagnetic. All waves
have the same characteristics and exhibit certain behaviors, subject to the constraints of conservation of energy.
Note: the use of e.g. denotes examples which may be used for in-depth study. The terms for example and such as denote
material which is testable. Items in parantheses denote further definition of the word(s) preceding the item and are testable.
Students can observe and describe transmission of various forms of energy.
Major Understandings:
4.1a All energy transfers are governed by the law of conservation of energy.*
4.1b Energy may be converted among mechanical, electromagnetic, nuclear, and thermal
forms.
4.1c Potential energy is the energy an object possesses by virtue of its position or
condition. Types of potential energy include gravitational* and elastic*.
4.1d Kinetic energy* is the energy an object possesses by virtue of its motion.
4.1e In an ideal mechanical system, the sum of the macroscopic kinetic and potential
energies (mechanical energy) is constant.*
4.1f In a nonideal mechanical system, as mechanical energy decreases there is a
corresponding increase in other energies such as internal energy.*
4.1g When work* is done on or by a system, there is a change in the total energy* of the
system.
4.1h Work done against friction results in an increase in the internal energy of the system.
4.1i Power* is the time-rate at which work is done or energy is expended.
(Note: Items with asterisks* require quantitative treatment per the Reference Table for Physics. Asterisks following individual words refer to the
preceding word or phrase only; asterisks appearing after the final period of a sentence refer to all concepts or ideas presented in the sentence.)
PERFORMANCE
INDICATOR 4.1
Physics 15
4.1j Energy may be stored in electric* or magnetic fields. This energy may be transferred
through conductors or space and may be converted to other forms of energy.
4.1k Moving electric charges produce magnetic fields. The relative motion between a
conductor and a magnetic field may produce a potential difference in the conductor.
4.1l All materials display a range of conductivity. At constant temperature, common
metallic conductors obey Ohm’s Law*.
4.1m The factors affecting resistance in a conductor are length, cross-sectional area,
temperature, and resistivity.*
4.1n A circuit is a closed path in which a current* can exist. (Note: Use conventional
current.)
4.1o Circuit components may be connected in series* or in parallel*. Schematic diagrams
are used to represent circuits and circuit elements.
4.1p Electrical power* and energy* can be determined for electric circuits.
Students can explain variations in wavelength and frequency in terms of the source of the
vibrations that produce them, e.g., molecules, electrons, and nuclear particles.
Major Understandings:
4.3a An oscillating system produces waves. The nature of the system determines the
type of wave produced.
4.3b Waves carry energy and information without transferring mass. This energy may
be carried by pulses or periodic waves.
4.3c The model of a wave incorporates the characteristics of amplitude, wavelength,*
frequency*, period*, wave speed*, and phase.
4.3d Mechanical waves require a material medium through which to travel.
4.3e Waves are categorized by the direction in which particles in a medium vibrate
about an equilibrium position relative to the direction of propagation of the wave, such
as transverse and longitudinal waves.
4.3f Resonance occurs when energy is transferred to a system at its natural frequency.
4.3g Electromagnetic radiation exhibits wave characteristics. Electromagnetic waves
can propagate through a vacuum.
4.3h When a wave strikes a boundary between two media, reflection*, transmission,
and absorption occur. A transmitted wave may be refracted.
4.3i When a wave moves from one medium into another, the wave may refract due to a
change in speed. The angle of refraction (measured with respect to the normal) depends
on the angle of incidence and the properties of the media (indices of refraction).*
4.3j The absolute index of refraction is inversely proportional to the speed of a wave.*
PERFORMANCE
INDICATOR 4.1
continued
PERFORMANCE
INDICATOR 4.3
4.3k All frequencies of electromagnetic radiation travel at the same speed in a vacuum.*
4.3l Diffraction occurs when waves pass by obstacles or through openings. The wavelength
of the incident wave and the size of the obstacle or opening affect how the wave
spreads out.
4.3m When waves of a similar nature meet, the resulting interference may be explained
using the principle of superposition. Standing waves are a special case of interference.
4.3n When a wave source and an observer are in relative motion, the observed frequency
of the waves traveling between them is shifted (Doppler effect).
PERFORMANCE
INDICATOR 4.3

posted by James @ 7:13 AM