10km/h it has more momentum

What does it mean to have momentum?

Use momentum in a sentence. When is it commonly used?

What does it mean in that context? How does the common use relate to the

science use?

What does it mean to have momentum?

Talk to your partner: Use momentum in a sentence. When is

it commonly used? What does it mean in that context? How does the common use relate to the

science use?

Momentum

Momentum is a commonly used term in sports. A team that has the momentum is on the move and is going to take some effort to stop.

Momentum is a physics term; it refers to the amount of motion that an object has.

A sports team that is on the move has the momentum.

If an object is in motion (on the move) then it has momentum.

Predict, Observe, Explain Which will hit the floor faster?

Which hit the floor first? Why did this happen? What affects the rate at which an object falls?

16.2g aluminum 53.58g copper

Momentum Defined

Momentum is defined as "mass in motion." All objects have mass; so if an object is moving,

then it has momentum The amount of momentum that an object

has depends upon two things Mass (how much stuff there is) Velocity (how fast the stuff is moving)

Momentum depends upon the variables mass and velocity.

The formula is: P=mv (p is momentum)

Momentum’s Units P=m•v The units for momentum would be mass

units times velocity units. The standard metric unit of momentum is

the kg•m/s. Other units that are acceptable (though not

conventional) include kg•km/hr, and g•cm/s.

To find your momentum units, use the units from your equation.

Find the unit P=m•v

A 2,000kg car travels 3m/s kg*m/s

A 4g ball rolls .2km/h g*km/h

A 333,000kg jet travels 885km/h kg*km/h

SpeedMeasuring motion

Calculating Speed

Speed (S) = distance traveled (d) / the amount of time it took (t).

Formula:

S = d/t

Units for speed

Variable, but will always be a distance unit / a time unit

Ex. Cars: km/h Jets: km/h Snails: cm/s Falling objects: m/s

Calculating speed

If I travel 100 kilometers in one hour then I have a speed of…

100 km/h

If I travel 1 meter in 1 second then I have a speed of….

1 m/s

S = d/t

Average speed

Average Speed is usually NOT CONSTANT Ex. Cars stop and go regularly Ex. Runners go slower uphill than

downhill

Average speed = total distance traveled/total time it took.

Calculating Average Speed

It took me 1 hour to go 40 km on the highway. Then it took me 2 more hours to go 20 km using the streets.

Total Distance: 40 km + 20 km = 60 km

Total Time: 1 h + 2 h = 3 hr

Ave. Speed: total d/total t = 60 km/3 h = 20 km/h

Average Speed =Total distance

Total time

Question

I ran 1000 m in 3 minutes. Then ran another 1000 m uphill in 7 minutes. What is my average speed? A) 100 m/min B) 2000 m/min C) 10 m/min D) 200 m/min E) 20 m/min

Total Dist. = 1000 m + 1000 m = 2000 m

Total Time = 3 min + 7 min = 10 min

Ave speed = total dist/total time =

2000m/10 min = 200 m/min = D

Velocity

Velocity – the SPEED and DIRECTION of an object.

Example: An airplane moving North at 855 km/h A missile moving towards you at 200 m/s

Question

What is the difference between speed and velocity?

Speed is just distance/time. Velocity includes direction as well.

But…

In this class we will pretty much use them interchangeably.

Just know there’s a difference

Graphing Speed: Distance vs. Time Graphs

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1200

1400

1600

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Dis

tanc

e (k

m)

Time (hr)

Phoenix

Denver

Graphing Speed: Distance vs. Time Graphs

Graphing Speed: Distance vs. Time Graphs

3 h

600 km

Graphing Speed: Distance vs. Time Graphs

3 hours

600 m

Different Slopes

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Time (hr)

Dis

tan

ce (

km

)

Run = 1 hr

Run = 1 hr

Run = 1 hr

Rise = 0 km

Rise = 2 km

Rise = 1 km

Slope = Rise/Run= 1 km/1 hr= 1 km/hr

Slope = Rise/Run= 0 km/1 hr= 0 km/hr

Slope = Rise/Run= 2 km/1 hr= 2 km/hr

Question

Below is a distance vs. time graph of my position during a race. What was my AVERAGE speed for the entire race?

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Time (hr)

Dis

tan

ce (

km

)

Average Speed = Total distance/Total time = 12 km/6 hr

= 2 km/hr

Run = 6 hr

Rise = 12 km

Measure by Slope first to last data point

Question

What does the slope of a distance vs. time graph show you about the motion of an object?

It tells you the SPEED

Question

Below is a distance vs. time graph for 3 runners. Who is the fastest?

Leroy is the fastest. He completed the race in 3 hours

What happened here?

Distance goes down? What’s that mean?

Distance goes down?

0 .2 .4 .6 .8 1.0 1.2

To go to A.T.

Math practice done and assignment turned in

Exit Question

What is the difference between velocity and speed?

Your turn Practice the math on the back of your worksheet Get a computer and finish packet from last week Vocab – make sure you research the PHYSICS

meaning, and write the definition in your own words. Note where you found the definition. GOOGLE IS NOT A SOURCE.

To go to A.T. have at least the vocab for this weeks quiz done Acceleration Momentum Velocity Force Add to list

Acceleration

Acceleration = speeding up

Acceleration – the rate at which velocity changes Can be an:

Increase in speed Decrease in speed Change in direction

Types of acceleration

Increasing speed Example: Car speeds up at green light

Decreasing speed Example: Car slows down at stop light

Changing Direction Example: Car takes turn (can be at

constant speed)

screeeeech

Question

How can a car be accelerating if its speed is a constant 65 km/h?

If it is changing directions it is accelerating

Calculating Acceleration

If an object is moving in a straight line

Time

SpeedInitialspeedFinalonAccelerati

__

Units of acceleration:m/s2

Acceleration is simply expressed as velocity per seconds. And Velocity as meter per seconds. So the SI notation is m*s*s.

Calculating Acceleration

0 s 1 s 2 s 3 s 4 s

0 m/s 4 m/s 8 m/s 12 m/s 16 m/s

2/4

4

/0/16

__

sm

s

smsmTime

SpeedInitialSpeedFinalonAccelerati

FinalInitial

Question

A skydiver accelerates from 20 m/s to 40 m/s in 2 seconds. What is the skydiver’s average acceleration?

2/10

2

/20

2

/20/40

__

sm

s

sm

s

smsmTime

speedInitialspeedFinalAccel

Graphing Acceleration

Can use 2 kinds of graphs Speed vs. time Distance vs. time

Graphing Acceleration:Speed vs. Time Graphs

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Time (s)

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ee

d (

m/s

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1) Speed is increasing with time = accelerating2) Line is straight = acceleration is constant

Graphing Acceleration:Speed vs. Time Graphs

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d (

m/s

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1) In Speed vs. Time graphs:Acceleration = Rise/Run = 4 m/s ÷ 2 s = 2 m/s2

Run = 2 s

Rise = 4 m/s

Graphing Acceleration:Distance vs. Time Graphs

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1) On Distance vs. Time graphs a curved line means the object is accelerating.

2) Curved line also means your speed is increasing. Remember slope = speed.

Question

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Sp

ee

d (

m/s

)

Above is a graph showing the speed of a car over time.1) How is the speed of the car changing (speeding up,

Slowing down, or staying the same)?2) What is this car’s acceleration?

1) The car is slowing down2) Acceleration = rise/run = -6m/s ÷3s = -2 m/s2

Run = 3 s

Rise = -6 m/s

PositivePositive acceleration acceleration

Negative Negative accelerationacceleration

Question:

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(m

)

1) Which line represents an object that is accelerating?

The black and red lines represent a objects that are accelerating. Black is going a greater distance each second, so it must be speeding up. Red is going less each second, so must be slowing down

Remember: in distance vs. time graphs: curved line = accelerating, flat line = constant speed

Question: Hard one

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m/s

)

Above is a graph showing the speed of a car over time.1)What would a distance vs. time graph for thislook like?

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Time (s)

Dis

tan

ce (

m)