Motion, Speed, Velocity, and Acceleration
Motion; Speed;
Velocity; Acceleration
What Is Motion?
Motion
is when an object changes place or
position. To properly describe motion, you
need to use the following:
•
Start and end position?
•
Movement relative to what?
•
How far did it go?
•
In what direction did it go?
What Is Speed?
Speed
is the distance an
object travels in a certain
amount of time.
To calculate speed, you
use the following formula:
Speed (s) =
Distance (d)
Time (t)
Speed Math Problem
Suppose you ran 2 km in 10
min. What is your speed?
S =
2 km
= 0.2 km/min
10 min
Another Problem
What is the speed of a car traveling
144 km in 90 minutes per hour?
________________ km/h
In miles per hour? __________ mph
Solution
Km/hour:
How many hours are in 90 minutes? There are 60
minutes in 1 hour; therefore 90 minutes equals 1.5
hours
144 km
= 96 km/h
1.5 hours
Miles per hour:
How many km are in a mile? 1 km = 0.621 miles;
therefore 144 km = 89.424 miles
89.424 miles
= 59.616 mpg or 59.6 mpg
1.5 hours
Ways To Calculate Speed
Constant speed
is when
you are traveling at the
same rate of speed, such
as 55 mph constantly on
a highway.
Average speed
is taking
the total distance
traveled, and dividing by
the total time it takes.
Used for calculations that
involve changing speed.
Instantaneous speed
is
the speed at any one
given point in time.
Average Speed
What is the
AVERAGE
speed of the
bass boat
depicted in
the graph?
Average Speed
Average
speed
is
taking the
total distance
traveled (0 to
125 meters),
and dividing
by the total
time (1 to 9
seconds) it
takes.
Average Speed =
125 meters
= 15.6 m/s
8 seconds
Instantaneous Speed
What is the
instantaneous
speed of the
bass boat at
t=7 seconds?
Instantaneous Speed
Instantaneous
speed is speed
at any given
point in time.
At 7 seconds,
the distance is
85 meters;
therefore the
IS is
Instantaneous Speed =
85 meters
= 12.1 m/s
7 seconds
Speed Graphs
•
In what time period is the bass boat speeding up?
•
In what time period is the bass boat slowing down?
•
When is the speed NOT changing?
Graphing Speed
Speed is usually graphed
using a line graph, and it
depicts the distance and
time.
•
Time
is the independent
variable, and thus is
ALWAYS on the x-axis.
•
Distance
is the
dependent variable, and
is ALWAYS on the y-axis.
Graph the following data
D
i
s
t
a
n
c
e
30
40
50
60
90
T
i
m
e
15
20
30
50
60
Distance over Time
Velocity
Velocity
is the speed of an object, but the direction is also
included. It is calculated the same as speed, but you must
include a direction in your answer.
Example: the bass boat was moving 12 mph toward the
north.
Velocity Problem
Indicate which of the following are velocities:
a.
125 cm/sec
b.
30 km/h northwest
c.
350m/sec north
d.
520 km/h
Velocity Problem
Indicate which of the following are velocities:
a.
125 cm/sec
no
b.
30 km/h northwest
yes
c.
350m/sec north
yes
d.
520 km/h
no
Acceleration
Acceleration
is the
rate of change of
velocity. A change in
velocity can be either
a change in speed, or
direction, or both.
Deceleration
is when
acceleration has a
negative value.
Acceleration
The formula for calculating acceleration is:
Acceleration (a) =
final velocity (v
f
) – initial velocity (v
i
)
time (sec)
The unit for velocity, in this case, is
m/s/s OR m/s
2
Acceleration Math Problem
A jet starts at rest at the end of a
runway and reaches a speed of 80
m/s in 20 s. What is its
acceleration?
Acceleration Math Problem
A jet starts at rest at the end of a runway
and reaches a speed of 80 m/s in 20 s.
What is its acceleration?
Acceleration (a) =
final velocity (v
f
) – initial velocity (v
i
)
time (sec)
a =
80 m/s – 0 m/s
= 4 m/s
2
20 sec
Acceleration Math Problem
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=
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2
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m
/
s
Homework Assignment
Copy this down – Assignment is due
Friday:
Handout on calculating speed and
velocity
Forces
A
force
is a push or pull
that one body exerts on
another. A force can
cause the motion of an
object to change. There
are two types of forces:
•
Balanced force
– one in
which the net force is
zero.
•
Unbalanced force
– one
in which the net force
has a numerical value.
Forces
+ 1 force
- 1 force
Balanced Force
Net force = 0
+ 1 force
- 2 force
Unbalanced Force
Net force = -1
+ 1 force
+ 1 force
Unbalanced Force
Net force = +2
Inertia
Inertia is the tendency of
an object to resist any
change in motion. Put in
another way, if an object
is moving, it will keep
moving until an outside
force acts on it.
Inertia is related to mass:
the greater the mass of
an object, the greater its
inertia.
Newton’s 1
st
Law of Motion
Newton’s 1
st
Law
is also known
as the law of inertia. It says:
An object in motion will stay in
motion, and an object at rest will
stay at rest, unless acted upon
by an outside force.
Example: if you are approaching
a fence on a running horse, and
the horse suddenly stops, you
will keep going forward over the
horse’s head unless you are
wearing a seatbelt! (I don’t care
who you are – that’s funny!)
Inertia
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!
The End!
Motion is when an object changes its place or position. To describe motion accurately, consider the start and end position, movement relative to a reference point, distance traveled, and direction. Speed refers to the distance traveled per unit of time and can be calculated using the formula speed (s) = distance (d) / time (t). Explore various speed calculation problems and concepts such as constant speed, average speed, and instantaneous speed. Additionally, delve into scenarios like determining the speed of a car and calculating average speed from a graph depicting a bass boat's motion.
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Presentation Transcript
Motion; Speed; Velocity; Acceleration
What Is Motion? What Is Motion? Motion is when an object changes place or position. To properly describe motion, you need to use the following: Start and end position? Movement relative to what? How far did it go? In what direction did it go?
What Is Speed? What Is Speed? Speed is the distance an object travels in a certain amount of time. To calculate speed, you use the following formula: Speed (s) = Distance (d) Time (t)
Speed Math Problem Speed Math Problem Suppose you ran 2 km in 10 min. What is your speed? S = 2 km = 0.2 km/min 10 min
Another Problem Another Problem What is the speed of a car traveling 144 km in 90 minutes per hour? ________________ km/h In miles per hour? __________ mph
Solution Solution Km/hour: How many hours are in 90 minutes? There are 60 minutes in 1 hour; therefore 90 minutes equals 1.5 hours 144 km = 96 km/h 1.5 hours Miles per hour: How many km are in a mile? 1 km = 0.621 miles; therefore 144 km = 89.424 miles 89.424 miles = 59.616 mpg or 59.6 mpg 1.5 hours
Ways To Calculate Speed Ways To Calculate Speed Constant speed is when you are traveling at the same rate of speed, such as 55 mph constantly on a highway. Average speed is taking the total distance traveled, and dividing by the total time it takes. Used for calculations that involve changing speed. Instantaneous speed is the speed at any one given point in time.
Average Speed Average Speed Bass Boat Speed 140 What is the AVERAGE speed of the bass boat depicted in the graph? 125 120 100 100 Distance (meters) 85 80 65 65 65 60 50 40 20 20 0 0 1 2 3 4 5 6 7 8 9 10 Time (seconds)
Average Speed Average Speed Bass Boat Speed 140 Average speed is taking the total distance traveled (0 to 125 meters), and dividing by the total time (1 to 9 seconds) it takes. 125 120 100 100 Distance (meters) 85 80 65 65 65 60 50 40 20 20 0 0 1 2 3 4 5 6 7 8 9 10 Time (seconds) Average Speed = 125 meters = 15.6 m/s 8 seconds
Instantaneous Speed Instantaneous Speed Bass Boat Speed 140 What is the instantaneous speed of the bass boat at t=7 seconds? 125 120 100 100 Distance (meters) 85 80 65 65 65 60 50 40 20 20 0 0 1 2 3 4 5 6 7 8 9 10 Time (seconds)
Instantaneous Speed Instantaneous Speed Bass Boat Speed 140 Instantaneous speed is speed at any given point in time. At 7 seconds, the distance is 85 meters; therefore the IS is 125 120 100 100 Distance (meters) 85 80 65 65 65 60 50 40 20 20 0 0 1 2 3 4 5 6 7 8 9 10 Time (seconds) Instantaneous Speed = 85 meters = 12.1 m/s 7 seconds
Speed Graphs Speed Graphs Bass Boat Speed 70 65 65 65 60 50 50 Distance (meters) 45 40 30 20 20 15 10 0 0 0 1 2 3 4 5 6 7 8 9 10 Time (seconds) In what time period is the bass boat speeding up? In what time period is the bass boat slowing down? When is the speed NOT changing?
Graphing Speed Graphing Speed Speed is usually graphed using a line graph, and it depicts the distance and time. Bass Boat Speed 70 65 65 65 60 50 50 Distance (meters) 45 Time is the independent variable, and thus is ALWAYS on the x-axis. Distance is the dependent variable, and is ALWAYS on the y-axis. 40 30 20 20 15 10 0 0 0 1 2 3 4 5 6 7 8 9 10 Time (seconds)
Graph the following data Graph the following data Distance Distance Time Time 15 20 30 50 60 30 40 50 60 90
Distance over Time Distance over Time 100.00 90.00 80.00 70.00 Distance (m) Distance (m) 60.00 50.00 40.00 30.00 20.00 10.00 0.00 15.0 20.0 30.0 50.0 60.0 Time (min)
Velocity Velocity Velocity is the speed of an object, but the direction is also included. It is calculated the same as speed, but you must include a direction in your answer. Example: the bass boat was moving 12 mph toward the north.
Velocity Problem Indicate which of the following are velocities: a. 125 cm/sec b. 30 km/h northwest c. 350m/sec north d. 520 km/h
Velocity Problem Indicate which of the following are velocities: a. 125 cm/sec b. 30 km/h northwest c. 350m/sec north d. 520 km/h no yes yes no
Acceleration Acceleration Acceleration is the rate of change of velocity. A change in velocity can be either a change in speed, or direction, or both. Deceleration is when acceleration has a negative value.
Acceleration Acceleration The formula for calculating acceleration is: Acceleration (a) = final velocity (vf) initial velocity (vi) time (sec) The unit for velocity, in this case, is m/s/s OR m/s2
Acceleration Math Problem Acceleration Math Problem A jet starts at rest at the end of a runway and reaches a speed of 80 m/s in 20 s. What is its acceleration?
Acceleration Math Problem Acceleration Math Problem A jet starts at rest at the end of a runway and reaches a speed of 80 m/s in 20 s. What is its acceleration? Acceleration (a) = final velocity (vf) initial velocity (vi) time (sec) a = 80 m/s 0 m/s = 4 m/s2 20 sec
Acceleration Math Problem Acceleration Math Problem A skateboarder is moving in a straight line at a speed of 3 m/s and comes to a stop in 2 sec. What is his acceleration? a = 0 m/s - 3 m/s = -1.5 m/s2 2 m/s
Homework Assignment Homework Assignment Copy this down Assignment is due Friday: Handout on calculating speed and velocity
The End! The End!
