# AP Week 2 8.15.2011-8.19.2011

Document Sample

```					AP Physics
Week of August 15, 2011-August 19, 2011

Monday August 15, 2011

Objective: TLW go into greater depth on the differences between accuracy and precision as well
as more experience with the Metric and British measurement systems.

Arizona State Standards: Strand 1: Concept 2: PO 4, Concept 3; PO 1, PO 2

Warm Up: The accepted value of gravity at the Earth’s surface is 9.8m / s 2 . Bob was working on
a lab where he calculated gravity at Earth’s surface to be 9.23m / s 2 , 9.26 m / s 2 , and 9.21m / s 2 .
Susie performed a different experiment and calculated the gravity at Earth’s surface to be
8.9m / s 2 , 10.1m / s 2 , and 9.7m / s 2 . Who had the more accurate experiment and who had the
more precise experiment?

Main Content: The learners will work on a lab that explores the differences between accuracy
and precision

Wrap Up: Learners will write on a half sheet of paper two things that they learned from the lab.

Homework: Finish Lab as well as homework Chp 1 Problems; 3, 5, 9, 21, 23, 40, 48, 57 Due
Wednesday, August 17,2011

Tuesday, August 16, 2011

Objective: TLW begin to discuss one dimensional motion (position, speed, velocity, acceleration)

Arizona State Standards:

Warm Up: The Learners will be asked to explain the differences between speed and velocity if
there are any.

   Explain what one dimensional motion is
   Go over what position/distance (displacement) means and the average distance
o Positive vs. negative
o  =delta (means change in)
o x  x2  x1
o Magnitude-absolute value of displacement/distance
   Vector quantities vs. scalar quantities
o Vectors-both magnitude and direction
o Scalar-just magnitude no direction associated
   Speed and velocity
o Speed-scalar quantity telling you the magnitude of how fast you are going
o   Velocity-vector quantity telling you the magnitude AND direction of how fast you
are going and where
o   Time = t
o   Average velocity (time to run a mile, etc)
x x2  x1
    vavg       
t   t2  t1
   Another way to define average velocity (for linear velocities) is
v f  vi
vavg               .
2
o   Average Speed (nascar how fast the cars are going through the turns, speed limit
signs)
total distance
    savg 
t
o   Instantaneous Velocity
 Your velocity at an exact moment in time
 Asks students for examples of this (gps, speedometer)
dx
   Defined as v 
dt
o   Acceleration
 When an objects velocity changes, then the object goes through an
acceleration (deceleration is still accelerating in then negative direction).
v v2  v1
   Average acceleration is aavg               
t t2  t1
   Instantaneous acceleration is defined just like instantaneous velocity, only
dv
this time it is the derivative of the velocity with respect to time or a       .
dt
   This can also be defined as the second derivative of the position or
dv d  dx  d 2 x
a     
dt dt  dt  dt 2
   Constant Acceleration
 Such as gravity (which we will be mostly dealing with) is when
v  vo v  vo
a  aavg                
t 0     t
o   Kinematics equations
 Using the definition of constant acceleration we can rearrange this to have
our first kinematics equation
v f  vo
a
t
      at  v f  vo
v f  vo  at
    We can do this same thing for the average velocity
x f  xo
vavg 
t
   vavg t  x f  xo
x f  xo  vavg t
   We also know that from our other average velocity equation
v f  vo
vavg               substituting this into the previous equation will yield
2
 v f  vo 
 t  xo   v f  vo  t
1
    x f  xo  
 2                 2
   Well we just figured out what final velocity was so lets substitute
1
x f  xo 
2
  vo  at   vo  t  xo  1  2vo  at  t
2
again!
1
x f  xo  vot  at 2
2

Wrap Up: The learner will define instantaneous vs. avg quantities

Homework: Finish Chp. 1 Problems; 3, 5, 9, 21, 23, 40, 48, 57 Due Wednesday, August 17,2011

Wednesday, August 17, 2011

Objective: TLW further their development of kinematics equations as well as analyze and solve
kinematics problems based on information given.

Arizona State Standards:

Warm Up: Which of these situations show a change in velocity; A car driving 60 mph comes to
at stop at a light, a car driving 40 mph turns a corner at 40 mph, and/or a satellite orbits earth
at a constant speed.

x  t   Ct n
   Derivative of a power is dx
 nCt n1
dt
dx                                                   3t
o    Take      for the following equation x  t   5t 3  2t 2   4
dt                                                   2
   Negative acceleration does not necessarily mean slowing down. 2 different ways to get
negative acceleration
o Decrease of speed in the + direction
o Increase the speed in the – direction
   Positive acceleration does not necessarily mean speeding up. 2 different ways to get
positive acceleration
o Increase of speed in the + direction
o Decrease of speed in the – direction
   Eliminating acceleration in kinematics equation
1
v f  vo  at x f  xo  vot  at 2
2
v f  vo
a
t
1  v f  vo  2
x f  xo  vot             t
o
2 t 
1         1
x f  xo  vot  v f t  vot
2         2
1      1
x f  xo  vot  v f t
2      2
x f  xo   vo  v f  t
1
2
   Eliminating starting velocity

v f  vo  at       x f  xo 
1
2
 vo  v f  t
vo  v f  at

o    x f  xo 
1
2
 v f  at  v f  t
x f  xo   2v f  at  t
1
2
1
x f  xo  v f t  at 2
2
   Final kinematics equations (constant acceleration)
1
x f  xo  vot  at 2
2
v f  vo  at
o   v f 2  v0 2  2a  x f  xo 

x f  xo 
1
2
 vo  v f  t
1
x f  xo  v f t  at 2
2
   Free Fall Acceleration
o Free fall acceleration is when an object accelerates at a constant rate (meaning no
air resistance). On earth, this rate at which we accelerate is g or gravity.
   This acceleration is independent of the object’s mass or shape.
   Example bowling ball and feather.
   Note: Do not thing g is 9.8 m         it is in fact 9.8 m        it is a positive
s2                         s2
number.

   Example Problems
o I move at a constant speed, covering 1 meter every second for 5 seconds in the
negative direction. Draw a graph representing this motion.
o Starting at the origin, I walk in a positive direction, covering a meter every 3
seconds. I take 3 seconds to stop and turn, and return to my beginning position at
the same rate. Draw a graph representing this motion.
o In a qualifying two-lap heat, a race car covers the first lap with an average speed
of 90 mi/h. Can the driver take the second lap at a speed such that the average of
the two laps is 180 mi/h? Explain (use definition of velocity v=d/t and solve for t.
find total time and time for first lap and see how much time is left.)
o Bob beats Judy by 10m in a 100-m dash. Bob, claiming to want to give Judy an
equal chance, agrees to race her again but to begin from 10m behind the starting
line. Does this really give Judy an equal chance? (again use definition of velocity
v=d/t. Find both Bob’s and Judy’s time velocity for first race. Then take this
velocity and find the time it takes for the second race for each competitor.)
o   The position of a particle moving along an x axis is given by x t   12t 2  2t 3 ,
where x is in meters and t is in seconds. Determine (a) the position, (b) the
velocity, (c) the acceleration of the particle at t=3.0s
 (d) what is the maximum positive coordinate reached by the particle and
 (e) at what time is it reached.
 (f) what is the maximum positive velocity reached by the particle
 (g) at what time is it reached
 (h) what is the acceleration of the particle at the instant the particle is not
moving (other than at t=0)
 (i) Determine the average velocity of the particle between t=0 and t=3.

Wrap Up:

Homework:

Friday August 19, 2011

Objective: TLW practice their new found understanding of 1-dimensional motion.

Arizona State Standards:

Warm Up: Jules Verne in 1865 proposed sending people to the moon by firing a space capsule
from a 220-m long cannon with a final velocity of 10.97 km/s. What is the acceleration of this
space capsule? Express your answer in g’s, where 1 g = 9.8 m/s2.

o    Bob beats Judy by 10m in a 100-m dash. Bob, claiming to want to give Judy an
equal chance, agrees to race her again but to begin from 10m behind the starting
line. Does this really give Judy an equal chance? (again use definition of velocity
v=d/t. Find both Bob’s and Judy’s time velocity for first race. Then take this
velocity and find the time it takes for the second race for each competitor.)
o    The position of a particle moving along an x axis is given by x t   12t 2  2t 3 ,
where x is in meters and t is in seconds. Determine (a) the position, (b) the
velocity, (c) the acceleration of the particle at t=3.0s
 (d) what is the maximum positive coordinate reached by the particle and
 (e) at what time is it reached.
 (f) what is the maximum positive velocity reached by the particle
 (g) at what time is it reached
 (h) what is the acceleration of the particle at the instant the particle is not
moving (other than at t=0)
 (i) Determine the average velocity of the particle between t=0 and t=3.
o    The minimum distance required to stop a car moving at 35 mi/hr is 40ft. What is
the minimum stopping distance for the same car moving at 70 mi/hr assuming
the same rate of acceleration?
o    A student throws a set of keys vertically upward to her sorority sister, who is in a
window 4m above. The keys are caught 1.5 seconds later by the sister’s
outstretched hand.
 a. With what initial velocity were the keys thrown?
 b. What was the velocity of the keys just before they were caught?
o    A speeder moves at a constant 15 m/s in a school zone. A police car starts from
rest just as the speeder passes it. The police car accelerates at 2 m/s2 until it
reaches a maximum velocity of 20 m/s. Where and when does the speeder get
caught?

Wrap Up:

Homework: CHP 2. 3, 4, 5, 61, 78, 79

```
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
 views: 7 posted: 12/18/2011 language: English pages: 6
How are you planning on using Docstoc?