Unit 1 Concept 1 Notes - Describing Motion

Motion

• Motion: when an object changes its position.

– Dependent on the reference point.

• Reference point: an indicator that orients

you; the place from where you measure,
record, or witness an event.
– Ex. Consider the reference point when describing

the motion of a car.

Measuring Motion

• Distance: (d) how far an

object has moved.
– Can be measured in m,

in, ft, mi, etc.

• Displacement: (Δx)

distance and direction of
an object’s change in
position; difference from
starting to ending point.
– Ex. If a runner runs

around a 400 m track and
ends where they started,
they have traveled a
distance of 400 m, but
have been displaced 0 m.

Fill in the Blanks

Fill in the Blanks

d = 50 + 20
d = 70 m

Δx = 50 – 20
Δx = 30 m North

Example #1

If a soccer player runs after his
opponent 50 m North, then turns
around and chases him 20 m
South, what is his distance and
displacement? Use the picture
to the right to help you.

d = ?
Δx = ?

50 m

20 m

Δx

Measuring Motion

• If an object travels at a right

angle, the Pythagorean
theorem is used to find the
displacement.

Sometimes finding displacement isn’t as easy.

a

b

=c

– c (the hypotenuse of the right triangle) would be

the displacement (Δx)

– Note: This will not need to be used every time

you find displacement!!

​

​a^2 + b^2 = c^2

Fill in the Blanks

Fill in the Blanks

Δx

Example #2

a^2 + b^2 = c^2

a

b

=c

A delivery truck drives 4 miles
West before turning right and
driving 6 miles North to make a
delivery. Find the delivery truck’s
distance and displacement.

a = 4 miles

b = 6 miles

c = Δx = ?

4 miles

6 miles

d = 4 + 6
d = 10 mi

a^2 + b^2 = c^2

4^2 + 6^2 = c^2

16 + 36 = c^2

52 = c^2

7.21 = c

√

√

c = 7.21

Δx = 7.21 mi
Northwest

​6 miles

• ​Take some time to work on Unit 1 p. 6 Practice: Distance vs. Displacement.

• To exit the presentation, click the gear icon in the top left corner of the screen. Then click save and exit.

• Once you have completed the assignment, click on the link for this presentation again and then hit resume attempt.

Measuring Motion

• Speed: (s) the distance an object travels per

unit of time.
– Can be measured in m/s, mi/hr, ft/min, km/hr, etc.

s =

t

d

Calculating Speed

s = 2 km
10 min

s = 0.2 km/min

s = ?
d = 2 km
t = 10 min

s = d
t

Example #3: Suppose you ran 2 km
in 10 min. With what speed did you
run?

t = 2000 m
343 m/s

t = 5.83 s

Calculating Speed

Example #4: Sound travels at 343 m/s through

dry air. If a lightning bolt strikes the ground 2,000 m away from you, how long will it take for
the sound to reach you?

​

​t = ?
s = 343 m/s
d = 2000 m

Two Types of Speeds

• Average speed: total distance traveled divided by

total time traveled.
– Ex. If I’m driving to Clemson to watch the National Championship

football team play, it is a total distance of 300 miles from my house.
If it takes me 5 hours to get there, my average speed is 60 mi/hr.

• Instantaneous speed:

the speed at any given
point – what shows up on
your speedometer.
– Ex. On my trip to Clemson, at

some points on the highway my
instantaneous speed is 70 mi/hr.
At stoplights, my instantaneous
speed is 0 mi/hr.

Velocity

• Velocity: (v) the speed of an object and the

direction of its motion.
– Speed can remain constant and velocity change if

the object is changing direction.

– Calculated the same as speed, just must include

direction in your answer!!

v =

t

d

Practice Time

1.

A girl is training to run a 5k race. If she
runs a trial race in 0.5 hours, what is her average
speed?

2.

An elevator at a museum can travel 210 m
upwards in 35 s. What is the elevator’s velocity?

3.

How far does a car travel in .75 hrs if it is moving
at a constant speed of 45 mi/hr?

4.

If a motorcycle is moving at a constant speed
down the highway of 40 km/hr, how long would it
take the motorcycle to travel 10 km?

Answer: s = 10 km/hr

Answer: v = 6 m/s upwards

Answer: d = 33.75 mi

Answer: t = 0.25 hr

• ​​Take some time to work on Unit 1 p. 7 Practice: Speed and Velocity.

• To exit the presentation, click the gear icon in the top left corner of the screen. Then click save and exit.

• Once you have completed the assignment, click on the link for this presentation again and then hit resume attempt.

Graphing Motion

• Slope: the steepness of a line.

– Calculated as rise = Δy

• On a distance vs. time graph, this means…

Graphs can visually help us to understand an object’s motion.

run Δx

– Calculated as rise = Δy = distance

run Δx time

• Therefore on a distance vs. time graph, the slope = speed.

Multiple Choice

Choose the graph that matches the following description of motion: the object is moving at a constant speed, away from the reference point.

Multiple Choice

Choose the graph that matches the following description of motion: the object is moving at a constant speed, coming towards the reference point.

Multiple Choice

Choose the graph that matches the following description of motion: the object is speeding up, due to the line becoming steeper.

Multiple Choice

Choose the graph that matches the following description of motion: the object is slowing down, due to the line leveling out.

Graphing Motion

The object
is moving

at a

constant
speed,

away from

the

reference

point.

The object
is moving

at a

constant
speed,
coming

towards the
reference

point.

The object
is speeding
up, due to

the line

becoming
steeper.

The object
is slowing
down, due
to the line
leveling

out.

Multiple Choice

Choose the graph that shows an object not moving.

Multiple Choice

Choose the graph that shows an object moving at a constant speed, stopping, then speeding up.

Graphing Motion

Sketch a graph that would show an object not moving.

Sketch a graph that would show an object moving at a

constant speed, stopping, then speeding up.

• You have now completed the notes for Concept 1 of Unit 1.​​​

• Take some time to work on Unit 1 p. 10 Practice: Motion Graphs.