Kinematics Study Guides
You'll need to be able to recognize these (and various permutations) on sight:

Motion Graph Analysis

Derivatives & Integrals & Graphs (oh my)
Parabolic Motion
 
 

1) Is the object moving in one or two dimensions?

  • Find x components
    • Physics convention is that motion to the right on the x axis is positive
    • Physics convention is that motion the the left on the x axis is negative
  • Find y components
    • Physics convention is that motion upwards on the y axis is positive
    • Physics convention is that motion downwards on the axis is negative
  • We won't work in the z direction
  • Two dimensional problems require analyzing motion in one dimension first and then finishing by completing an analysis of motion in the second dimension.... it can get a bit tricky.

2) Gravity ONLY works in the Y dimension

  • Gravity is ALWAYS present in vertical motion problems
  • Gravity is totally absent in x-motion problems
  • We will use 9.81 m/s/s as our class value for acceleration here on the surface of the Earth. Please keep in mind that on the AP test and on warmup problems we will often just round that to 10. m/s/s

3) Air Friction is *usually* absent in our problems (along with wind, changes in atmospheric density and other minutiae we will ignore). Look for specific indications that air friction is NOT being ignored

FORUMLAE OBJECTUS (You MUST commit these to working memory ASAP)

Subscripts:

f = final, i = initial.

Keep in mind-- some sources use the subscript o ("naught") as initial, other sources prefer subscripts 1 for the first value and 2 for the final, or subsequent values)

variables:

  • v = velocity
  • a = acceleration
  • t = time
  • x = displacement in the x dimension
  • y = displacement in the y dimension

1) vf = vi +at

2) vavg = (vi + vf)/2

3*) xf = xi + vit + 1/2at2

4*) vf2 - vi2 = 2ax

5*) (v)(t) = x (We learned this one in 6th grade and it's really easy to forget, make sure you don't do that. It's also very easy to use when you shouldn't....be careful)

* these show motion in the x direction, replace x with y to use the same formulae in the vertical direction

NOTE: Sig figs will ALWAYS cost you 1/2 point if you get them wrong. You don't get any points for getting them right since you should know them already.