Warm Up 9-12
What does the slope of a distance vs. time graph
represent?
What is the standard (SI) unit for distance?
What is the standard (SI) unit for time?
What is the standard (SI) unit for speed?
What does ‘SI Unit’ stand for?
Speed
Speed is the rate at which an object moves, or
changes position.
It is the distance
that an object
travels over a
period of time.
𝐃𝐢𝐬𝐭𝐚𝐧𝐜𝐞
𝐒𝐩𝐞𝐞𝐝 =
𝐓𝐢𝐦𝐞
The standard unit for distance is meters (m)
The standard unit for time is seconds (s)
Speed
Anything that is not at rest has speed,
there are 3 types:
1) Constant Speed: Speed that does not change
2) Instantaneous Speed: Speed at a specific point
3) Average Speed: The TOTAL distance divided by
the TOTAL time
Think About It!
Where in real life do you see Constant Speed?
Where do you see Instantaneous Speed?
Where do you see Average Speed?
How did you measure speed on a distance vs.
time graph?
Velocity =
𝐃𝐢𝐬𝐩𝐥𝐚𝐜𝐞𝐦𝐞𝐧𝐭
𝐓𝐢𝐦𝐞
The standard unit for displacement is meters (m)
The standard unit for time is seconds (s)
Velocity
Velocity is a speed with direction
Speed vs. Velocity
Speed: Bruce does a flying
kick at 11 mph
Velocity: Bruce does a flying
kick at 11 mph to the left
Acceleration
Acceleration is the rate of change in velocity
Acceleration includes:
-Speeding Up
-Slowing Down
and the weird one…
-CHANGING DIRECTION
Fast Write
Is it possible for a car to accelerate with the
cruise control on?
Timer
Acceleration
Just like velocity, there is
positive and negative
acceleration
Positive acceleration is
speeding up AWAY from the
starting point
Negative acceleration is
speeding up TOWARDS the
starting point
Acceleration
Slowing down is
known as
deceleration
Moving at a
constant speed is
known as having
0 acceleration
𝐕𝐟 − 𝐕𝐢
𝐀𝐜𝐜𝐞𝐥𝐞𝐫𝐚𝐭𝐢𝐨𝐧 =
∆𝐭
𝐕𝐟 is the final velocity of the object
𝐕𝐢 is the initial (starting) velocity of the object
∆𝐭 is the change in time
The standard unit for acceleration is m/s2
Let’s Practice!
If a police officer scans my car with a radar
detector, what type of speed has he/she
measured?
Instantaneous
Speed!
Let’s Practice
If you take a trip to Dallas for the weekend and it
takes you approximately 5 hours to travel 350
miles. What was your average speed?
70 mph
Let’s Practice
A train travels 160 miles for 1.6 hours heading
South from New York to Washington D.C. What
is the train’s velocity?
100 mph
South
Let’s Practice!
How far could you travel if you drive at a constant
speed of 30 mph for 6 hours?
How far could you travel if you drive going a little
faster at 75 mph but travel for only 5.5 hours?
Which one covers more distance?
How much more?
Let’s Practice
Suppose you are planning on driving to San
Antonio (280 miles) next month for a mini
vacation. You are a law abiding citizen and are
planning to drive the speed limit at a constant
speed of 70 mph. How long will it take you to
get there?
4 hours
Let’s Practice
Driver A is driving in circles at a constant speed of 6
mph.
Driver B started at rest and is now backing out of a
parking spot.
Driver C has his gas pedal to the floor but is doing a
burnout.
Which of the above drivers are accelerating?
A and B
Let’s Practice
An airplane starting from rest at one end of the
runway acquires its takeoff speed of 600 m/s in
8 s. What is its acceleration?
75 m/s2
Let’s Practice
Suppose that at point A, a car has a velocity of 5
m/s and by the time the car reaches point B it
has increased its velocity to 20 m/s. It takes the
car 5 seconds to go from point A to point B.
What is its acceleration?
3 m/s2