A. Kinematics Book notes

FYI: This is a sample of concepts in chapter 2. You need to take your own textbook notes (due on 9/24/01) but I hit a few highlights here. This is the format you should use!

Further, your notes will encompass both chapters 2 and 3 since A. Kinematics covers both chapters.

VOCABULARY:

-Mechanics: The study of motion and what produces and affects motion (p. 33)

-Kinematics: A subsection of mechanics which deals only with describing motion (ex. Acceleration, velocity…etc)

-Dynamics: A subsection of mechanics which deals with the causes of motion (ex. Force, friction, work, energy, power, momentum)

-Distance: The length of an entire path from start to finish.

-Displacement: The straight line distance between the start and finish point.

YOU MUST DO ALL OF THE VOCAB WORDS!!!!!!!!!!!!!!!!

KEY CONCEPTS:

Mathematical Symbols:

Distance has units of m.

x = distance in the horizontal direction (+x values move right. –x values move left)

y = distance in the vertical direction. (+y values move up. –y values move down)

Velocity has units of m/sec or m/s

v_o = initial velocity (often the value for this is zero – if the object is at rest to start)

v_f (or just v) = final velocity

Dv = change in velocity (Dv is ALWAYS found: v_f-v_o)

v = Average velocity (ALWAYS has a bar over it. No bar means INSTANTANEOUS

VELOCITY.)

v = Dv/2. WHY? Because you are taking an average of your initial and final velocities

Acceleration has units of m/sec² or m/s².

a = acceleration. (same rules applies to a as did v. See variations on v above. Example,

average a = Da/2, a_o is initial acceleration.…etc.)

g = acceleration due to gravity on the earth which is always 9.8 m/s2.

Vectors vs. Scalars: A vector quantity has both magnitude (a number) and a direction. A scalar quantity has only magnitude but the direction is not specified. (p. 33-35)

Scalars: distance, speed, mass, weight, work, time, energy

Vectors: Displacement, Velocity, Acceleration, Momentum, Impulse, force

In the textbook you will find bold symbols are vectors. Non-bold symbols are scalar.

Graphing:

The first word is on the y-axis, the second is on the x-axis (Example: “Imagine you are looking at a distance vs. time graph”…. Distance is y-axis, time is x-axis)

Need to know graphing facts:

To find the slope of a line, use the formula Dy/Dx

The slope of a distance vs. time graph gives you the average velocity (see p. 40)

The slope of a tangent line to a point on a distance vs. time graph is instantaneous vel.

The area under the curve of a velocity vs. time graph gives you displacement.

Fast conversion tricks:

Km/hr into m/sec: Multiply the Km/hr quantity by 0.278 (see p. 43)

m/sec into Km/hr: Divide the m/sec quantity by 0.278

Free Fall:

- When you throw and object up, it has an apex velocity (apex means “top of the flight”) of 0 m/sec. (Think about it: It goes up, stops and then turns around and comes right back down – LOOK OUT BELOW!)

- An object returns to the earth at the same speed from which it was thrown, but in an opposite direction. (Think about it: What do you think happens to bullets?)

- When you throw an object, it ALWAYS undergoes a DOWNWARD acceleration of 9.8 m/sec². This is true for the ENTIRE flight, even when it has an apex velocity of

0 m/sec. The Earth never stops pulling! Gravity never takes breaks!

KEY FORMULAS:

COPY ALL OF THE FORMULAS FROM P. 57 HERE. YOU MUST COPY ALL OF THE FORMULAS FROM EACH SECTION

EXAMPLE PROBLEMS:

ANY TOUGH ONES FROM THE CHAPTER THAT YOU DON’T UNDERSTAND OR THINK YOU MIGHT FORGET, PUT THEM HERE. OR AT LEAST MAKE NOTE THAT ON P. 53 THERE IS A FREE FALL EXAMPLE….ETC. Don’t feel obligated to write all of the example problems. They will remain in the book for future reference. But working them out in your own handwriting sometimes offers worlds of insight!