• The position of an object is how far away it is from a reference point (frame of reference)
• Scalar - just magnitude (how much)
• Vector - magnitude and direction (how much and which way)
• Displacement is the change in position … (final position – original position)
• Displacement is a vector quantity and can be positive or negative.
• Average velocity is the displacement (change in position) divided by the change
in time (time interval).
• Velocity is how fast and in what direction.  Speed is only how fast.
• v = d/t {which also gives us: t= d/v and d = vt
• This equation only works for constant or average velocity.
• For constant/uniform velocity, a position-time graph yields a straight line. The slope of that line is equal to the velocity.
• Instantaneous velocity is the velocity at a specific moment in time.  If there is acceleration, instantaneous velocity is not the same as average velocity.

Ch 2-2: Acceleration

• Acceleration is the change in velocity divided by the change in time. 
• Acceleration can be determined graphically from a velocity-time graph. 
• If the velocity-time graph is a straight line, then the acceleration is constant (uniform) and is equal to the slope of the line. 
•For uniform acceleration, the velocity-time graph is linear. 
•Ch 2-2 contains 4 basic equations that use 5 variables. The 5 variables are: 
      a ... which stands for acceleration; for free-falling objects, a = g = -9.8 m/s/s 
      t ... which stands for time, or the time interval (change in time) 
      d ... which stands for displacement, or change in position 
      v_i  ... which stands for the initial velocity at the beginning of the time period in question 
      v_f  ... which stands for the final velocity at the end of the time period in question 
•The 4 equations are given below. Each uses 4 variables. The problems will contain 3 known/given variables and 1 unknown variable. You need to pick the equation that contains those 4 (3 known / 1 unknown) variables. You may have to rearrange the equation so that the unknown is by itself on one side of the equation. 
       Equation               Variables
     v_f = v_i  + at           v_f , v_i, a, t
      d = ½ (v_f  + v_i) t     d, v_f, v_i, t
      d = v_it + ½at²         d, v_i, t, a
    v_f² = v_i² + 2ad          v_f, vi, a, d
•Steps to solving a problem. 
 1) Read the problem. 
 2) Identify the given variables and the unknown variable it is asking for. 
 3) Select the proper equation to use. 
 4) If the unknown is not by itself on one side (preferably the left), then you should rearrange the equation to make it so. It is possible to put in the numbers and then rearrange it, but this will turn out to be more difficult in the long run. 
 5) Do the math required to solve for the unknown. 
 6) If there is a second part to the problem, you can probably use any of the remaining three equations, since you will now know 4 of the 5 variables. 
 7) Check to make sure your answer is reasonable (i.e. if you're 3 given variable are in single digits, an answer in the millions might be a sign that something is wrong). Also, check to see that you have the correct units (i.e. if you are finding a velocity and your answer is in meters, something is wrong somewhere). 

Ch 2-3: Free-falling

•The acceleration of gravity near the earth is -9.80 m/s/s. By making it negative, you are saying that upward motion is the positive direction, and downward is negative.