Transcript Kinematics

Do Now:
 Graph the following data in a velocity-time graph. Find the
acceleration.
 Use a new sheet of paper and please turn in your Do Now’s
from last week .
Time (s)
Velocity (m/s)
1
4
2
8
3
12
4
16
Kinematics
the branch of classical mechanics that
describes the motion of bodies (objects)
and systems
The Big Four
Example #1
An airplane while in flight, accelerates from
a velocity of 21.0 m/sec at a constant rate
of 3.00 m/sec2 over a total of 535 meters.
1. Which kinematics variables are stated in
this problem?
2. Which kinematics equation would you
use to solve this problem?
3. What was its final cruising velocity?
Example
While gliding down a steep hill, a bike rider
experiences constant acceleration. After 4.50
seconds, he reaches a final velocity of 7.50
m/sec. The bike's displacement was 19.0
meters.
1. Which kinematics variables are stated in
this problem?
2. How fast was the bike traveling when it
first started down the hill?
3. Which kinematics equation did you use to
solve this problem?
Practice
Use the rest of class to practice
doing problems from the
worksheet “One-Dimensional
Kinematics.” This will be due
Wednesday.
Area under a V/T Graph
 The area under the
curve of a v/t graph is
equal to the distance
covered
Do Now ( 6 min)
A car accelerates uniformly from rest to
a final speed of 56 m/sec in 10
seconds.
1. How far does it travel during this
period of acceleration?
2. What acceleration did the car
experience?
Hypothesize:
Create a hypothesis for the following
question. Be sure to BACK UP YOUR
RESPONSE.
Question: What kind of motion results from
gravity? In other words, how does gravity
act on falling objects? Be sure to describe
velocity, acceleration, displacement, etc.
When you are done, share with your elbow
partner!
Mini-Lab:
 We will do a 10 minute mini-lab on gravity.
 Your goal: Describe the motion due to gravity.
 Measure the time and distance for each of the 10 trials you
drop the ball.
1
 Use the formula d  at 2 to solve for the acceleration!!!
2
 When your group is finished, find the average and record
your data on the class chart
Do Now (10/5):
While gliding down a steep hill, a bike
rider experiences constant acceleration.
After 4.50 seconds, he reaches a final
velocity of 7.50 m/sec. The bike's
displacement was 19.0 meters.
1. Which kinematics variables are stated
in this problem?
2. How fast was the bike traveling when
it first started down the hill?
And the acceleration is….
The Acceleration due to Gravity
 The same for every object
 Bigger planets, stars, etc. have more
gravity
 On Earth, the absolute value is always
g=9.8 m/s2
 Freefall: an object being acted on only by
gravity
Solving Free Fall Acceleration Problems
Up is
positive
Use Big Four
Kinematics Equations
Replace a with g
In your system, take
up to be positive
Down is negative – so
g= - 9.8m/s2
Example #1
You drop a ball from a 5 m window.
1. What are the kinematics variables
you know?
2. How long does it take to hit the
ground?
3. What is the ball’s final velocity right
before it hits?
Do Now (10/6):
You drop a ball from a window. It
takes 2.4 s to hit the ground.
1. What are the kinematics
variables you know?
2. What is the ball’s final velocity
right before it hits the ground?
3. What is the height of the
window?
Maximum Height
 At the objects maximum height, the
velocity is 0 m/s
 when asked to find the maximum
height or how long it takes to reach
the maximum height, vf= 0 m/s
Do Now (10/7):
A ball is thrown straight up with a speed
of 4.6 m/s. How long does the ball take
to reach its maximum height?
1. What kinematic variables are you
given?
2. How long does it take the ball to
reach its maximum height?
3. What is the ball’s maximum height?
Collected Work:
Pass in your Do Now’s and
your homework. #’s 9 and
10 on your homework will
be BONUS questions –
don’t worry about them!
Practice
Use the rest of class to
practice doing problems
on the worksheet “FreeFall Acceleration.” This
sheet is due Friday.
Do Now (10/10):
A ball is thrown straight up with a speed
of 30 m/s. How long does the ball take
to reach its maximum height?
1. What kinematic variables are you
given?
2. How long does it take the ball to
reach its maximum height?
3. What is the ball’s maximum height?
Practice
Use the rest of class to
practice doing problems
on the Test#2 Review.”
This sheet is due Thursday.
Do Now:
You drop a ball from a 10 m window.
What are the kinematics variables you know?
2. How long does it take to hit the ground?
3. What is the ball’s final velocity right before it hits?
1.
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Do Now:
 Begin working on the Pre- lab questions
worksheet. If you don’t have one, raise your
hand.You won’t be able to answer every
question yet but some of them you can
answer today.
 Please take out your labs and turn them in
 Keep your Kinematics worksheets – they will
be due on the day of the test
New Unit: Forces
First Topic:
Newton’s
Three Laws
Newton’s First Law
 First law: Every body remains in a state of rest or uniform
motion (constant velocity) unless it is acted upon by an
external unbalanced force.
 Net force – sum of all the forces acting on an object
Newton’s Second Law
 Second law: A body of mass m subject to a force F
undergoes an acceleration a that has the same direction as the
force and a magnitude that is directly proportional to the
force and inversely proportional to the mass, i.e., F = ma.
Summary:
F=ma
Freefall acceleration:
 We will do a 10 minute mini-lab on gravity.
 Last week in lab we determined that gravity causes objects to
accelerate when dropped. How did we know?
 Your goal: find the acceleration due to gravity.
 Measure the time and distance for each of the 10 trials you
drop the ball.
1 2
 Use the formula d  at to solve for the acceleration!!!
2