what is physics? motion

Unit 1 - Constant Motion

Ms. Levine 1

September 2016

Motion

Part 1: Constant Speed

What is Physics?

Physics is the study of the physical world (energy and matter) and how they are

related.


Ms. Levine 2

September 2016

• What is the purpose of these motion maps?

• What is it showing us?

Connor runs quickly at a constant speed to the east. Madelyn runs slowly with a constant speed to the west. Draw a motion map for each below. (use the lines to help you)

Connor

Madelyn

Create your own motion map

What do you think about when you hear the word motion?


Ms. Levine 3

September 2016

In this unit, we will be discussing movement in a straight line.

What do we need to know to describe motion?

What do we need to know to describe motion?

• direction (left-right, forward-backward, north-south)

• units of measure

• a starting point (what happens if the starting point were to change?

Frame of Reference

- the place from which motion is observed and measured

Frame of Reference Video!.mp4

Frame of Reference #1.mp4

Let's watch a couple short videos to help us better understand this concept.

What is speed?

the distance traveled divided by the time it took to travel that distance

so to calculate speed we need distance and time

How far is a second?.mp4

SI Units

distance -

time -

speed -

Speed and Distance doesn't require us to define where we started from and where we ended up.

it just measures how far we traveled and how long it too to travel that far

Much of Physics is about knowing where something is and how its position changes with time


Ms. Levine 4

September 2016

Displacement

-x

+y

-y

+x

PennsylvaniaNew Jersey

For instance, if you drive 60 miles from Pennsylvania to New Jersey

and then traveled 20 miles back towards Pennsylvania,

How many miles did you travel?

How far are you from where you started? In what direction?

What is displacement?

Displacement - the change in position ( x)

- how far you are from where you started

Δx = Xf - Xo

Distance can only be a positive value since it is impossible to travel a negative distance.

xf xo-x

+y

-y

+xxo xf-x

+y

-y

+x

DisplacementHowever, displacement can be positive or negative since you can end up to the right or left of where you started.

Displacement is positive. Displacement is negative.

Vectors and Scalars

Scalar - a quantity that has only a magnitude (number or value)

Vector - a quantity that has both a magnitude and a direction

Quantity Vector Scalar

Time

Distance

Displacement

Speed

Which of the following are vectors? Scalars?

Ans

wer

1 How far your ending point is from your starting point is known as:

A distance

B displacement

C a positive integer

D a negative integer

2 A car travels 60m to the right and then 30m to the left. What distance has the car traveled?

+x- x

Ans

wer


Ms. Levine 5

September 20163 You travel 60m to the right and then 30m to the

left. What is the magnitude (and direction) of our diplacement?

+x- x

Ans

wer

4 Starting from the origin, a car travels 4km east and then 7 km west. What is the total distance traveled?

A 3 km

B -3 km

C 7 km

D 11 km

Ans

wer

5 Starting from the origin, a car travels 4km east and then 7 km west. What is the net displacement from the original point?

A 3 km west

B 3 km east

C 7 km west

D 11 km east

Ans

wer

6 You run around a 400m track. At the end of your run, what is the distance that you traveled?

Ans

wer

7 You run around a 400m track. At the end of your run, what is your displacement?

Ans

wer

Average Velocity

Speed is defined as the ratio of distance and time

Velocity is defined as the ratio of displacement and time

s = dt

ΔxΔtv = Average velocity = time elapsed

displacement

Average speed = distance traveledtime elapsed

Speeds are always positive, since speed is the ratio of distance and time; both of which are always positive.

But velocity can be positive or negative, since velocity is the ratio of displacement and time; and displacement can be negative or positive.


Ms. Levine 6

September 2016

8 Which of the following is a vector quantity?

A time

B velocity

C distance

D speed

Ans

wer

9 Average velocity is defined as change in ______ over a period of ______.

A distance, time

B distance, space

C displacement, time

D displacement, space

Ans

wer

10 You travel 60 meters to the right in 20 s; what is your average velocity?

Ans

wer

11 An elephant travels 60 meters to the left in 20 s; what is the average velocity?

Ans

wer

12 You travel 60 meters to the left in 20 s and then you travel 60 meters to the right in 30 s; what is your average velocity?

Ans

wer

13 You travel 60 meters to the left in 20 s and then you travel 60 meters to the right in 30 s; what is your average speed?

Ans

wer


Ms. Levine 7

September 2016

14 You run completely around a 400 m track in 80s. What was your average speed?

Ans

wer

15 You run completely around a 400 m track in 80s. What was your average velocity?

Ans

wer

16 You travel 160 meters in 60 s; what is your average speed?

Ans

wer

Let us transpose our motion maps to a position vs time graph.


Ms. Levine 8

September 2016

Now in reverse, a position vs time graph to a motion map.


Ms. Levine 9

September 2016

What does a position vs time graph look like of an object that is not moving? Moving at a constant velocity?

Draw below.

constant velocitymotionless

what is physics? motion

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