# Motion

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```					 Motion
Measuring Motion
What is motion?
A change in POSITION over TIME!
Motion
   Motion can be described in many ways
 Speed (Slow Motion, Fast forward, mph, etc)
 Direction (NSEW, Up, Down, Vertical, Against, etc)

 Acceleration

 Stopping

 Circular

 Periodic (think waves or tides)

 AND MANY MORE
Motion
   We will cover only a few types of motion in this
unit
 Speed
 Velocity

 Acceleration

 The effects of Gravity

 Force
What is speed?
   Speed refers a distance covered over an
amount of time.
   All objects in motion have speed.
   (Speed can also be called a rate.)
How is speed determined?
   Distance = speed X time
   Speed = distance
time
   Time = distance               D
speed
S       T
How to solve word problems
   Step 1: Underline important information
   Step 2: Write the Formula
   Step 3: Substitute the information you know
   Step 4: Perform calculations
   Step 5: Check that answer contains the correct
units
Speed Examples
    A car travels 300km in 6 hours. What is the
speed of the car?
2.   Speed = Distance/Time
3.   Speed = 300km/6hrs
Speed = 50km/hr
4.

Speed Examples
    What is the speed of a jet plane that flies
7200km in 9 hrs?

2.   Speed = Distance/Time
Speed = 7200km/9hrs
3.

4.   Speed = 800km/hr

Speed Examples
    How long will it take a car to drive 320 km if it
travels at 80km/hr?

2.   Time = Distance/Speed
3.   Time = 320km/80km per hr
Time = 4 hours

4.
Speed
   Speed that does not      Average Speed = Total Distance
Total Time
chance is called
CONSTANT SPEED

Total
Dist.

Ave             Total
Time
Speed
Speed Examples
    The speed of a cruise ship is 50km/hr. How
far will the cruise ship sail in 24 hours?

2.   Distance = Speed X Time
3.   Distance = 50km/hr X 24 hrs
Distance = 1200 km

4.
What is velocity?
   Velocity is SPEED
in a certain
DIRECTION
   Example:
 5 km/hr NW
 10mph against the
currant
 5m/s vertical
What is velocity?
   Velocities can be combined.
 Add the velocities if in the same direction
 Subtract the velocities if in opposite direction
Velocity
   A boat is traveling at a rate of 15km/hr
downstream. The speed of the current is
5km/hr. What is the combined velocity of the boat?

15km/h

5km/h

15km/hr + 5km/hr = 20km/hr
Velocity
   A boat is traveling at a rate of 15km/hr
upstream. The speed of the current is 5km/hr.
What is the combined velocity of the boat?

15km/h

5km/h

15km/hr - 5km/hr = 10km/hr
Velocity
   Negative velocities such as -20km/hr implies
direction (backing up or going in reverse)
Sample Questions
    What is the velocity of a car traveling south for
five hours over a distance of 250 miles?
2.   Velocity = Distance /Time
3.   Distance = 250miles/5 hrs
4.   Distance = 50 miles/hr, 50mph


Change in Velocity
   Acceleration is the rate of change of velocity.
   can be a change in speed or direction
   Formula: Final Velocity – Original Velocity
Time
   Formula: Vf – Vi
T
   Acceleration tells you how fast velocity is
changing
Acceleration
Distance -Time Graph

   Units for acceleration are              60

50

either km/hr/hr or                      40

Distance
Acceleration

m/sec/sec, commonly
30
Deceleration
20

referred to as:                         10

0

   Km/hr2 or m/s2                           0        20
Time
40

   Deceleration is a negative                                    Time
(s)
Distance
(km)
acceleration                                                      0            0

   A distance – time graph                                           2          0.5

is always a curve if                                              5
10
1
10
acceleration is present.                                         15           20
20           35
25           47
30           54
Acceleration Examples
   A roller coaster at the top of a hill is 10m/s, two
seconds later, at the bottom of the hill, it is
26m/s. What was the acceleration of the
coaster?
Acceleration = Final Velocity – Original Velocity
Time
Acceleration = 26m/s - 10m/s
2s
Acceleration = 8m/s2
Acceleration Examples
   Ethan comes off the top of the slide at 5m/s.
After 1.5 seconds he slides of the end and falls
into the sand at 8m/s. What was his
acceleration?
Acceleration = Final Velocity – Original Velocity
Time
Acceleration = 8m/s - 5m/s
1.5s
Acceleration = 2m/s2
Circular Motion
   The velocity is continuously changing because
the direction is continuously changing.
   An object in circular motion is accelerating even
though its speed may be constant.
Free Fall
   Gravity is the weakest known of the natural forces, only
becoming obvious with massive objects like planets and
stars.
   Common acceleration due to gravity is 10m/s2
or 9.8m/s2
   Free fall is an object falling under the influence
of gravity
Free Fall
   Formulas:
Velocity = at
Distance = at2/2
Free Fall
   Example:
A ball is dropped. It falls for 5 seconds before it hits
the ground. What is the velocity of the ball when it
hits the ground?
Velocity = at
Velocity = 9.8m/s2 X 5s
Velocity = 49m/s
Free Fall
   Example:
A ball is dropped. It falls for 5 seconds before it hits
the ground. How far above the ground was it
dropped?
Distance = at2/2
Distance = (9.8 m/s2)(5s)2 /2
Distance = (9.8 m/s2)(25s2 )/2
Distance = 245m/2
Distance = 122.5m
Free Fall
   Free Fall is when an object is moving
only due the acceleration of gravity
   Gravity (g) = 9.8m/s2
   Distance = gt2/2
Free Fall
   Bobby Sue drops a penny into a
wishing well. It falls 5 seconds
before she hears the plink. How
deep is the well?
distance = gt2/2
distance = (9.8m/s2)(5s)2/2
distance = (9.8m)(25)/2
distance = 122.5m
Free Fall
   Acceleration is a measure of
changing velocity
   As shown by the graph, the
velocity increases by 10m/s
every second the object falls.
Free Fall
   For objects starting at rest we can calculate the
final velocity of the object on impact.
   Final Velocity = (a * t) – Initial Velocity
   Final Velocity = (a * t) – 0m/s
   Final Velocity = a*t
of an object
dropped
Sample Problem
   Corky drops a water balloon from the roof of his house
onto an unsuspecting victim below. The balloon
narrowly missed the person below and explodes onto
the empty pavement after 7 seconds.
 How tall is Corky’s house?
Distance = at2/2
Distance = (9.8m/s2)(7s)2/2
Distance = (9.8m/s2)(49s2)/2
Distance = 480.2 m/2
Distance = 240.1 m
Sample Problem
   Corky drops a water balloon from the roof of his house
onto an unsuspecting victim below. The balloon
narrowly missed the person below and explodes onto
the empty pavement after 7 seconds.
 How fast is the balloon going when it impacts the
ground?
Vf = (a*t) – Initial Velocity
Vf = (10m/s2 * 7s) – 0m/s
Vf = 70 m/s (how fast? REALLY fast)

```
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