AP Physics - Semester Review

Bland introduction. Touch of humour unbeknownst to passive viewer.

TITLEBy: Chris Wilson

Friday, March 29, 13


Objective:~Use paper to get the area of the car

tire in contact with ground.~Use pressure-gauge to determine

pressure in tires.~Calculate approx. weight of car.

Compare with actual weight.




Distance vs. DisplacementBack in the day..

Displacement = distance between A & B.Distance traveled involves path.

Of above points, displacement is equal,regardless of path.


Speed vs. Velocity

The formula for calculating velocity is:

V = ∆d

∆t(aka)

Final Distance - Initial Distance

Final Time - Initial Time

Therefore, Path A has a velocity of 0.

Therefore, if Paths B and C were traveled in 5 seconds each, they would have the same velocity.


Acceleration

At point X, object is accelerating rightwards.At point Y, object is accelerating leftwards.

At point Z, object is accelerating rightwards.

An object rolls down a ramp and then around a turn.Determine acceleration at points X, Y, and Z.


Describing Motion with Diagrams

The object is accelerating at a rate of 0.2 m/s/s

Red shows velocity at certain given points.

Rightwards (or positive) acceleration evident.


Describing Motion with Graphs

Positive direction & positive accelerationPositive direction & negative acceleration

Negative direction & positive accelerationNegative direction & negative acceleration

Constant speeds versus acceleration (in negative or positive direction)


Graphical Analysis

At t = 1, acceleration slows from 40 m/s to 20 m/sAt t = 4, acceleration slows from 20 m/s to -20 m/s

Areas to pay attention to are squared in red (by me).


1-Dimensional Kinematics

Equations! Plug what you know to find out what you don’t.Xf = Xi + Vit + (1/2)at2

Final Distance

Initial Distance

Time

Acceleration/Gravity

Initial Velocity


Motion Problems with Equations

Velocity-time graph!Time is the x-axis, Velocity is the y-axis.

At time = 10, acceleration changes.

At time = 12, velocity is 0.

The big complex idea was an object’s velocity-time graph would be a very different (and yet related)

graph than the acceleration-time graph.Friday, March 29, 13

Inertia and Balanced Forces

Now we’re dealing with the forces.

Force of Friction (Ff or Ffrict) opposing theForce of Acceleration (Fa or Faccel).

Normal Force (Fn or Fnorm) opposing theForce of Gravity (Fg or Fgrav).

If all forces are balanced, the object isn’t accelerating.. but that doesn’t necessarily mean it isn’t moving!

Symbols:∑ = “sum of”


Newton’s 2nd Law and Free-Body Diagrams

Using Mathematica, some code and some formulae, we are able to let

Mathematica crank the numbers while we do the thinking.

Work smarter, not harder!

Mass is involved too!


Hollywood Physics

Take clip that involves Physics from a movie.Obtain data involving the Physics in the shot.

Crunch the data.Reach a solution.

Way cool.Friday, March 29, 13

Vectors and Projectiles

More displacement!

Ol’ Pythagorean’s Theorem to find the hypotenuse.Friday, March 29, 13

Pulley Problems

What? A tech school student that did some

work on paper?

Formulas with μ? That’s the coefficient of friction.

With these wonderful massless frictionless pulleys, we can use the mass of two blocks to do some odd (yet

simplex) math stunts.

Too add, or not to add μ? That is the question.Friday, March 29, 13

Vectors Addition

Usually, this is just careful use of Pythagorean’s Theorem. With the ideals involving 360º circle-based angles, of course.. and resultant vectors.

Sin/Cos/Tan to find the angle you’re looking for.

The math is simple. It’s the thinking that’s challenging.Friday, March 29, 13

Tension Forces

Tension, mainly seen with our pulley problems, resurfaces (literally and metaphorically).

The triangles are back, but they never really left.

Hanging up a picture with two nails/strings tied to the centerpoint of the top, which angle would have the least tension?


Incline Plane Analysis

Most everything combines, into... this.

Now that the object is on a slope, Fpara and Fperp are introduced. Fparallel is named because it’s parallel to the surface, Fperpendicular is named because it’s perpendicular to the surface.

We’re given some variables, and told to find the rest.


Thanks for.. watching?


Education

AP Physics - Semester Review