9th Physics

Waves, which exist in mechanical and electromagnetic forms, have various properties.

1. Waves can superimpose on one another, bend around corners, reflect off surfaces, be absorbed by materials they enter, and change direction when entering a new material. All these effects vary with wavelength. (AKSci - A.6)

o Determine, describe and demonstrate waves and their properties and the way they interact with matter. (for #1 and #2)

o Given the unmodulated frequency of an FM radio station, calculate the wavelength of its signal. (for #1 and #2)

2. Electromagnetic waves consist of: radio waves, microwaves, radiant heat, visible light, ultraviolet radiation, x rays, and gamma rays. These wave lengths vary from radio waves, the longest, to gamma rays, the shortest. In empty space, all electromagnetic waves move at the same speed--the "speed of light."(AKSci - A.6)

o Determine the velocity, wavelength, or frequency of ripple tank waves from values they have measured (or calculated) for the other two of these properties. (for #1 and #2)

o Given a sequential series of diagrams showing two transverse wave packets passing through one another on a string, draw the resulting superposition of the two wave pulses. (for #1 and #2)

Forces affect motion in a variety of ways.

A. Newton's Laws

1. The rate of change in motion of an object is proportional to the applied force and inversely proportional to the mass. (AKSci - A.6)

o Construct a force diagram for:a glider on a track attached to a freely hanging mass by a string hanging over a frictionless pulley or a mass in freefall near the surface of the earth.

o Predict the speed and direction of an object based on the force, time, and mass.

2. Whenever one thing exerts a force on another, an equal amount of force is exerted back on it. (AKSci - A.6)

o Construct a force diagram for:a glider on a track attached to a freely hanging mass by a string hanging over a frictionless pulley or a mass in freefall near the surface of the earth.

o Predict the speed and direction of an object based on the force, time, and mass.

3. The motion of an object is always judged with respect to some other object or point and so the idea of absolute motion or rest is misleading. (AKSci - A.6)

o Construct a force diagram for:a glider on a track attached to a freely hanging mass by a string hanging over a frictionless pulley or a mass in freefall near the surface of the earth.

o Predict the speed and direction of an object based on the force, time, and mass.

4. Newton's system was based on the concepts of mass, force, and acceleration. (AKSci - A.6)

o Construct a force diagram for:a glider on a track attached to a freely hanging mass by a string hanging over a frictionless pulley or a mass in freefall near the surface of the earth.

o Predict the speed and direction of an object based on the force, time, and mass.

B. Gravitational Force and Motion

1. Gravitational force is an attraction between masses. The strength of the force is proportional to the masses and weakens rapidly with increasing distance between them. (AKSci - A.3)

o Illustrate the relationship between mass and distance in relation to gravity.

2. The Newtonian model made it possible to account for such diverse phenomena as tides, the orbits of planets and moons, the motion of falling objects, and the earth's equatorial bulge. (AKSci - A.3, B.1)

o Apply Newton's laws to the diverse phenomena such as the earth's revolution of the sun.

C. Magnetic and Electric Forces

1. Magnetic forces are very closely related to electric forces and can be thought of as different aspects of a single electromagnetic force. Moving electric charges produce magnetic forces and moving magnets can produce electric forces. (AKSci - A.5)

o Conduct investigations to determine the properties of magnetism and electricity, how magnetic and electric forces are interrelated and describe how these properties play a role in technology and society.

o Compare mathematically the forces on two equal charges places "x" cm apart with those on the same charges when placed "2x" cm apart.

o Describe how changing the polarity of one charge affects the force on each charge.

2. A very small excess or deficit of negative charges in a material produces noticeable electric forces. (AKSci - A.5)

o Describe the relationship between oppositely charged particles and the resulting charges if the number of particles is unequal.

3. At the atomic level, electric forces between oppositely charged particles hold atoms and molecules together and thus are involved in all chemical reactions. On a larger scale, forces hold solid and liquid materials together and act between objects when they are in contact. (AKSci - A.5)

o Describe the relationship between oppositely charged particles and the resulting charges if the number of particles is unequal.

D. Pressure

1. Pressure is force divided by the area over which that force is applied. (AKSci - A.5)

o Explain the relationship between the area of an object and pressure applied, e.g., snowshoes vs. high heels, or a bed of nails vs. one nail.