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Physics

In Cambridge, we believe that by introducing students to physics as Freshman we are setting a foundation of knowledge that will allow them greater success in chemistry and biology. All 9th graders begin their time at CRLS in a heterogeneously grouped physics course, with an honors option.

In Grade 9 Physics, instructional time should focus on four critical areas:

  1. Forces and motion;
  2. Forms of energy;
  3. Electrical and magnetic energy; and
  4. Sound and light energy
Unit
Learning Goals
Motion
  • Explain why variables are vectors or scalars
  • Describe relationships between displacement, distance, velocity, speed, and acceleration
  • Find velocity or time given acceleration.
  • Describe the motion shown in a position-time or velocity-time graph with two or more segments (limited to constant velocity for position-time)
  • Interpret complex graphs Draw graphs of particular situations
  • Calculate acceleration (slope) from a velocity-time graph
  • Calculate distance traveled from a velocity-time graph in which the velocity changes uniformly
  • Describe how Newton’s Laws relate to common situations (i.e. seatbelts)
  • Recognize situations in which force or weight needs to be calculated as the first step of a problem
  • Solve simple two-step problems involving force and acceleration
  • Draw free-body diagrams of objects with forces in two-dimensions (right angles only). Use information from a problem to draw a free-body diagram.
  • Describe the affect of friction on the motion of an object
  • Make qualitative predictions about the motion of objects in collisions
  • Make predictions about how the gravitational force changes when mass and distance are changed
  • Conceptually describe forces in uniform circular motion
Electricity
  • Explain how electrons are transferred when objects are charged by friction or contact.
  • Explain the cause of polarization and give an example.
  • Understand how conductors and insulators affect the flow of electrons.
  • Determine the net charge on an ion.
  • Solve Coulomb’s Law formula for F with or without using scientific notation.
  • Qualitatively describe the relative effects of distance and charge on the electric force.
  • Describe the relationships between voltage, current and resistance. Apply V=IR to simple series circuits.
  • Draw schematic diagrams of both series and parallel circuits. Describe what happens when a circuit is open.
  • Build series and parallel circuits that include switches. Differentiate behavior of series and parallel circuits.
  • Describe conceptually the relationships between P, I, and V.
  • Solve two-step electric circuit problems involving P=IV and V=IR.
  • Recognize that moving electric charges produce magnetic forces and that moving a magnet produces an electric force.
  • Give examples of applications of electromagnetism (motors and generators).
Waves
  • Define pitch and volume with wave properties
  • Draw wave graphs with a given period, frequency and amplitude
  • Draw a graph of frequency versus wavelength
  • Describe the motion of the medium in transverse and longitudinal waves
  • Draw transverse and longitudinal waves
  • Compare sound graphs based on frequency (pitch) and amplitude (volume)
  • Change the frequency of a musical instrument
  • Give an example that compares the speed of sound in two materials
  • Explain and/or draw why frequency of a wave seems to change based on the motion of a sound source or receiver
  • Compare and contrast sound and light waves
  • Understand how the properties of mechanical and electromagnetic wave affect their use in outer space
  • Compare incident and reflected rays with respect to the normal
  • Relate the change in angle of a light ray to a change in speed of light.
  • Use c = fλ to solve for frequency or wavelength
  • For each section of the electromagnetic spectrum, describe at least one way that humans interact with it.
Energy
  • Explain with examples how work affects gains or losses in an object’s mechanical energy. Explain qualitatively how force and distance affect work done.
  • Solve two-step problems (i.e. calculating weight to solve for work or solving for work and then power)
  • Compare two objects based on their power output.
  • Solve two-step problems (i.e. compare the power of two objects or calculate work in order to find power)
  • Explain that total energy includes not only mechanical, but also includes thermal, chemical, electrical, etc.
  • Use PE = mgh to solve for mass, acceleration of gravity, or height.
  • Use KE = 1/2mv2 to solve for mass
  • Interpret and explain heat and temperature graphs
  • Distinguish between temperature and total heat energy
  • Explain what would happen to a material if its temperature dropped to absolute zero
  • Define specific heat
  • Use Q = mcΔt to solve for mass, specific heat, or change in temperature
  • Explain, on a molecular level, the process of heat transfer in each of the three methods
  • Identify factors that affect the rate of heat transfer (i.e. lightness or darkness of an object affects how well it absorbs radiation)