PHYSICS 221 Topic Checklist
UNIT 1
At the end of each chapter make sure that you are familiar with all the listed topics and most importantly that you can do the homework problems associated with them.
Chapter 1 Introduction Try to get a feeling for what physics is all about and what you will be learning this semester.
q Scientific Theories Know how scientific knowledge is acquired and codified into laws and theories.
q Units of Measurement Learn the metric prefixes micro m, milli m, centi c, kilo k, mega M.
q Significant Figures Be able to present results of measurements and calculations with the correct number of significant figures.
q Scientific Notation Be able to express numbers in both decimal and scientific form.
Chapter 2 The Study of Motion This is one of the most important chapters in the book. Be sure you master the concepts of displacement, velocity and acceleration .
q Average Speed The distance any object moves divided by the time it took to move that far.
q Units of Speed distance/time; m/s, mi/hr, etc.
q Unit Conversion Be able to change any quantity from one set of units to another.
q Scalars Quantities with magnitude only.
q Vectors Quantities with both magnitude and direction.
q Displacement A vector extending from the initial position to the final position of a moving object.
q Average Velocity A vector, defined as the displacement of an object divided by the time to undergo that displacement.
q Representation of Motion on a Coordinate System Learn to represent physical values such as position and velocity as mathematical variables referenced to a rectangular coordinate system. Use the delta symbol D, to denote the change of a quantity.
q Instantaneous Velocity The “actual” velocity at a specific moment as opposed to the average over an extended period of time.
q Acceleration The rate at which the velocity of an object changes.
q Constant Acceleration If an object moves in a straight line with a constant acceleration, the motion is said to be uniformly accelerated. In this case the average acceleration and the instantaneous acceleration are equal. The following very useful equations are valid in this situation. Note: In most physics books a quantity with no subscript is the final value, while the subscript o indicates the initial value of that quantity.
q Free Fall A body falling under the influence of gravity alone is a good example of uniformly accelerated motion. In metric units, this acceleration is approximately 9.80 m/s2 and is directed downward. The accepted symbol for this value is g.
q Problem Solving The most difficult aspect of a physics course is solving the problems. Problem solving is the application of abstract theory to practical situations and thus is the basis of modern technology. Be sure that you can do all the homework problems. You cannot pass the tests if you cannot do the homework.
Note: The material developed in this chapter will be used throughout the remainder of the course as well as next semester. It is worth the effort to master it now.
Chapter 3 Motion in Two or Three Dimensions In this chapter the concepts of displacement, velocity, and acceleration you learned in chapter two will be extended to the more realistic case of two and three dimensional motion. To do this you must learn to deal mathematically with vectors.
q Graphical Representation of Vectors Vectors are drawn on diagrams as arrows. The length of the arrow is proportional to the magnitude of the vector it represents.
q Graphical Addition of Vectors The resultant of two or more vectors can be found by drawing the original vectors tip to tail on a diagram. Their resultant is then drawn from the tail of the first vector to the tip of the last one. An alternative graphical method is to draw two vectors with their tails together and then use the vectors to construct a parallelogram. The resultant is drawn as the diagonal of the parallelogram.
q Graphical Subtraction of Vectors Reverse the direction of the second vector and then add.
q Analytic (mathematical) Representation of Vectors Vectors may be represented as either (a) Magnitude, Direction or (b) x and y Components
q Trig Functions Vector math involves some trigonometry. Learn to use the three basic trigonometric functions and the Pythagorean theorem.
q Vector Components The projections of the vector on the x and y axes.
q Vector Addition using Components Use the following procedure to add vectors. It is essential that you first draw a good diagram showing the approximate magnitude and direction of the vectors to be added.
· Resolve each vector into x and y components.
· Add all the x components together. This gives the x component of the resultant. Repeat for the y components.
· Calculate the magnitude and angle of the resultant.
q Relative Velocity The velocity of an object is always specified relative to some other point of reference, usually the Earth. If more than one reference is used in a problem then the equation relating the relative velocities is:
q Projectiles In projectile motion the horizontal and vertical motions are independent. The horizontal motion is characterized by constant velocity, and the vertical motion by a constant acceleration of value g. For an object projected horizontally it is convenient to use a coordinate system in which y is positive downward. In this case:
Chapter 4 Force and Motion This is another of the very important chapters. You will learn how the forces that act on a body control its motion. These laws are basic to all of the rest of physics.
q Force The mechanism by which objects act on one another is called force. For now think of force as one object pushing or pulling another. It is a vector quantity because it has magnitude and direction.
q Newton’s First Law If the resultant force acting on a body is zero, it will move in a straight line at a constant speed. This means that its acceleration is zero. Note that this situation includes the special case of motionlessness. Thus an object at rest either has no forces at all acting on it (unlikely) or the resultant of the forces that do act is zero.
q Newton’s Second Law If the resultant force on a body is not zero, it will accelerate. The acceleration is equal to the resultant force acting on the body divided by its mass. This is a very important law.
q Newton’s Third Law Force always occurs as an interaction between exactly two objects. The two objects always exert equal and opposite forces on each other.
q Units Learn the basic MKS, CGS and FPS systems of units.
|
|
MKS (or SI) |
CGS |
FPS ( British) |
|
distance |
meter (m) |
centimeter (cm) |
foot (ft) |
|
time |
second (s) |
second (s) |
second (s) |
|
mass |
kilogram (kg) |
gram (g) |
slug = lb s2/ft |
|
force |
Newton (N) = kg m/s2 |
dyne = g cm/s2 |
pound (lb) |
q Weight The weight of any object is the force exerted by gravity on the object. Always use force units when stating a weight. A body’s weight is not the same as its mass but it does depend on its mass.
q Sliding Friction This is the force that arises when one object slides or attempts to slide across another. This type of force always tries to oppose the sliding motion and has a magnitude that depends on the so called normal force pressing the surfaces together. The force also depends on the nature of the surfaces via a quantity called the coefficient of friction. If the bodies are trying to slide but not actually moving use the coefficient of static friction mS. If they are actually sliding use the coefficient of kinetic friction mK.
q Problem Solving Be able to solve force problems involving several forces, inclines, and friction.
Chapter 5 Circular Motion Many common situations involve circular or approximately circular motion. Examples include automobiles rounding curves and satellites in gravitational orbits.
q Centripetal Acceleration An object moving along a circular path always has acceleration associated with the fact that it is changing direction. This is called its centripetal acceleration and is directed toward the center of the circle. If its speed is v and the circle has radius r then the magnitude is:
q Centripetal Force It requires an unbalanced force to cause a body to move in a circle. Any force that results in circular motion is called centripetal force.
q Newton’s Law of Universal Gravitation Newton discovered that the force of attraction between any two bodies depends directly on their masses and inversely on the square of their separation.
where G is a universal constant whose value in MKS units is 6.67 x 10-11 Nm2/kg2
q Orbital Motion Newton’s law of gravity provides the theory behind all calculations of satellite motion. For example orbital speed and period are given by:
q Fundamental Forces in Nature Physicists believe that all the different kinds of activities we observe can be reduced to just four fundamental forces or interaction types. They are:
Gravitational It arises from the mass of the interacting bodies and is the weakest of the four forces. Nevertheless it is strong enough to hold the Earth, the solar system, our galaxy, in fact the whole universe together.
Electromagnetic This is a more powerful force that arises from the electric charges that most fundamental particles possess. The electronics industry exploits this force in all of its products. It is also the force that holds atoms and molecules together. Thus it is what holds us together.
Weak Force This force exists only at the nuclear level. It is responsible for one kind of radioactivity.
Strong Force This is also a nuclear force. It is the one responsible for the enormous energy released in nuclear reactors.