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What is Exciting About this Scene?. http://www.youtube.com/watch?v=MlD5NBnzFhE. JTPS. What are 3 words that come to mind when you think about Motion?. Chapter 3. Linear Motion. Description of Motion. instantaneous speed - the speed that something has at any one instance. - PowerPoint PPT Presentation
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http://www.youtube.com/watch?v=MlD5NBnzFhE
JTPS
What are 3 words that come to mind when you think about Motion?
Linear MotionLinear Motion
instantaneous speed - the speed that something has at any one instance
interval timecovered distance total = speed average
timedistance Speed
...or 70 miles/hour on the open road.
However, during this trip your instantaneous speed might have been 0 miles/hour at a stoplight...
1. What is the average speed of a cheetah that sprints 100 meters in 4 seconds?
2. How about if it sprints 50 m in 2 s?
miles/hour…………….mph
kilometer/hour……….km/h
meters/second……….m/s
furlongs/fortnight?
If a car moves with an average speed of 60km/h for an hour, it will travel a distance of 60 km. (a) How far would if travel if it moved at
this rate for 4 hours? (b) For 10 h? (c) Would it be possible for the car to have
an average speed of 60km/h and never exceed a reading of 60km/h?
Velocity = {speed with a direction}
Examples:
70 mph is a speed.
70 mph North is a velocity.
VelocityVelocity
Acceleration - rate of change in velocity due to change in speed or direction
AccelerationAcceleration
interval time velocityof change =on Accelerati
Example:• 9.8 meters/second2 downward
"She moves at a constant speed in a constant direction.”
Say the same sentence in fewer words.
Answer: “She moves at constant velocity.”
The speedometer of a car moving to the east reads 100km/h.
It passes another car that moves to the west at 100km/h.
Do both cars have the same speed?
Do they have the same velocity?
During a certain time, the speedometer of car reads a constant 60km/h.
Does this indicate a constant speed?
Constant velocity?
(a) acceleration and time.(b) velocity and time.(c) distance and time.(d) distance and acceleration.
(a) 10km/h(b) 20km/h(c) 30km/h(d) more than 30km/h
The slope of the distance-time graph is the velocity
Constant Velocity Changing Velocity
Distance VS. Time
The slope of the velocity-time graph is the acceleration.
Constant Acceleration Changing Acceleration
Velocity VS. Time
How To Graphically Represent Linear Motion
Depicting Motion
Coordinate System- Deciding where to place the measuring tape and when to start the timer.
Origin- Point where both variables are of value zero.
Coordinate System
Problem Solving Follow these steps to solve problems:
Read ProblemMake Diagram Identify Knowns Identify UnknownsChoose FormulaSolve (and Check)
Acronym R.D. KUFS (Mr. Hairston’s Rap Alias)
Practice Drawing Motion A bike travels at a constant speed of 4.0
m/s for 5 s. How far does it go?
Practice Drawing Motion A bike accelerates from 0.0 m/s to 4.0
m/s in 4 s. What distance does it travel?
Practice Drawing Motion A bike first accelerates from 0.0 m/s to
5.0 m/s in 4.5s. What is the acceleration of the bike?
A car travels southeast at 83 m/s. How long will it take the car to travel 633 m?
White Board Question
Describing Motion: The Kinematic Equations
DISCOVERING THE UNKNOWN
Kinematic Equations
advv
atvv
tvv
d
attvd
if
if
fi
i
2
2
2
1
22
2
d = displacement
vi = initial velocity
vf = final velocity
a = acceleration
t = time
2
21gtd
A truck having an initial velocity of 30 m/s accelerates uniformly at +3 m/s2.
a)What is its velocity after 4 seconds?
a)How far has it traveled in 4 seconds?
c) How fast is it moving after it has traveled 100 m from its original position?
d)How long did it take to travel the 100 m?
R.D. KUFS
Ima Hurryin is approaching a stoplight moving with a velocity of +30.0 m/s. The light turns yellow, and Ima applies the brakes and skids to a stop. If Ima's acceleration is negative (-)8.00 m/s2, then determine the displacement of the car during the skidding process. (Note that the direction of the velocity and the acceleration vectors are denoted by a (+) and a (–) sign).
56.3 m
Practice Problem Solving
Ben Rushin is waiting at a stoplight. When it finally turns green, Ben accelerated from rest at a rate of a 6.00 m/s2 for a time of 4.10 seconds. Determine the displacement of Ben's car during this time period.
50.4 m
Practice Problem Solving
Free Falling
What will you do when there’s nothing holding you back?
• An object is in free fall when the only force acting on it is the force of gravity
• The force of gravity points downward• Acceleration due to gravity is 9.8m/s2
• Air resistance ignored
Free FallFree Fall
To a physicist, the term "free fall" has a different meaning than it does to a skydiver. In physics, free fall is the (one-dimensional) motion of any object under the influence of gravity only - no air resistance or friction effects of any kind, whereas it is air resistance that makes skydiving a hobby rather than a suicide attempt!
An Object In Free Fall
You should also note that an object doesn't have to be falling to be in free fall - if you throw a ball upward its motion is still considered to be free fall, since it is moving under the influence of gravity.
An Object In Free Fall
• An object is in free fall when the only force acting on it is the force of gravity
• The force of gravity points downward
• Air resistance ignored
• Acceleration due to the force of gravity near the surface of Earth is downward and has a value of g = 9.8 m/s2
(note: g is just the magnitude of the objects acceleration)
• We have then the conditions of one-dimensional kinematics – straight line motion with constant acceleration.
Free Fall
(a) you drop an object from rest at t=0.
(b) velocity acquired = acceleration time v = g t
(c)
For Free Fall...For Free Fall...
timetimeonAccelerati21 = traveledDistance
2
21gtd
A ball is thrown vertically upward at 10 m/s. How high will it get, how long will it be in the air, and how fast will it be moving when it hits the ground.
Sample Problem
timedistance Speed
Velocity = {speed with a direction}
interval time velocityof change =on Accelerati
g = 9.8 m/s2 downward
Kinematic Equations
advv
atvv
tvv
d
attvd
if
if
fi
i
2
2
2
1
22
2
d = displacement
vi = initial velocity
vf = final velocity
a = acceleration
t = time
v = g t
Free FallFree Fall
2gt
21d