Homework Due Read 7.1-7.2, Do # 1-6 pg. 100 & POGIL

Tonight’s HW  

Read & Study 7.1-7.2, Do # 7-10 pg. 100Finish today’s POGIL if necessary

Do Now 

1. Put BOTH of your HW assignments TOGETHER in the In Box (stack them together – don’t need to staple)

2. #26, pg. 101: You can’t throw a raw egg against a wall without breaking it, but you can throw it at the same speed at a sagging sheet without breaking it. EXPLAIN (think…velocity change, stopping time, etc.)

• Momentum is a commonly used term in sports. • A team that has a lot of momentum is really on the

move and is going to be hard to stop. • Momentum is a physics term; it refers to the

quantity of motion that an object has. • If an object is in motion (on the move) then it has

momentum… like a sports team!!!• Momentum can be defined as "mass in motion." • All objects have mass; so if an object is moving,

then it has momentum - it has its mass in motion.

• The amount of momentum that an object has is dependent upon two variables: • how much stuff  (mass) is moving • and how fast the stuff is moving.

• Momentum depends upon the variables mass and velocity. 

• In terms of an equation, the momentum of an object is equal to the mass of the object times the velocity of the object.

MOMENTUM IS INERTIA IN MOTION

https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&docid=FO5yycKoWBD9nM&tbnid=sSYfTQtMPNaY8M:&ved=0CAQQjB0&url=http%3A%2F%2Fdesertraiders.blogspot.com%2F2011%2F11%2Fgaming-mass-x-velocity-momentum.html&ei=nuHLUvuVB6jSsATkyoGIDg&bvm=bv.58187178,d.eW0&psig=AFQjCNFsJa6c0psiGMMhSH-WE8y3H4QZwg&ust=1389179670782172

EGG TOSS - - BEFORE#26, pg. 101: You can’t throw a raw egg against a

wall without breaking it, but you can throw it at the same speed at a sagging sheet without breaking it. EXPLAIN

 In your notebooks, please:•WRITE:•What you THINK will happen (use words or pictures)•WHY you think it will happen •Think back to your HW last night and use key terms! (think…velocity change, stopping time, etc.)

COMPARING THROWING AT THE SHEET VS.

THE HYPOTHETICAL WALL (ASSUME I THROW THE EGG WITH THE SAME INITIAL VELOCITY)

1. When would the egg have the greatest MASS?

2. When would the egg have the greatest CHANGE IN VELOCITY?

3. When would the egg have the greatest STOPPING TIME?

4. When would the egg experience the greatest FORCE (aka when is it more likely to break?)

After considering the above questions, WRITE:• What ACTUALLY happened (use words or pictures)• WHY you think it happened • Use the above questions to guide your explanation of WHY it happened! • PREDICT the relationships or equations you think we will explore today.

COMPARING THROWING AT THE SHEET VS.

THE HYPOTHETICAL WALL (ASSUME I THROW THE EGG WITH THE SAME INITIAL VELOCITY)

1. When would the egg have the greatest MASS?

Same in both

2. When would the egg have the greatest CHANGE IN VELOCITY?

3. When would the egg have the greatest STOPPING TIME?

4. When would the egg experience the greatest FORCE (aka when is it more likely to break?)

COMPARING THROWING AT THE SHEET VS.

THE HYPOTHETICAL WALL (ASSUME I THROW THE EGG WITH THE SAME INITIAL VELOCITY)

1. When would the egg have the greatest MASS?

Same in both

2. When would the egg have the greatest CHANGE IN VELOCITY?

Same in both (same CHANGE! Final minus initial velocities…starts from the same initial velocity in both, and ends with a velocity of ZERO in both)

3. When would the egg have the greatest STOPPING TIME?

4. When would the egg experience the greatest FORCE (aka when is it more likely to break?)

COMPARING THROWING AT THE SHEET VS.

THE HYPOTHETICAL WALL (ASSUME I THROW THE EGG WITH THE SAME INITIAL VELOCITY)

1. When would the egg have the greatest MASS?

Same in both

2. When would the egg have the greatest CHANGE IN VELOCITY?

Same in both (same CHANGE! Final minus initial velocities…starts from the same initial velocity in both, and ends with a velocity of ZERO in both)

3. When would the egg have the greatest STOPPING TIME?

Sheet – more ‘give,’ ‘cushion,’ ‘softer,’ etc…think back to the discussion during the first part of the Do Now

4. When would the egg experience the greatest FORCE (aka when is it more likely to break?)

COMPARING THROWING AT THE SHEET VS.

THE HYPOTHETICAL WALL (ASSUME I THROW THE EGG WITH THE SAME INITIAL VELOCITY)

1. When would the egg have the greatest MASS?

Same in both

2. When would the egg have the greatest CHANGE IN VELOCITY?

Same in both (same CHANGE! Final minus initial velocities…starts from the same initial velocity in both, and ends with a velocity of ZERO in both)

3. When would the egg have the greatest STOPPING TIME?

Sheet – more ‘give,’ ‘cushion,’ ‘softer,’ etc…think back to the discussion during the first part of the Do Now

4. When would the egg experience the greatest FORCE (aka when is it more likely to break?)

Wall!

COMPARING THROWING AT THE SHEET VS.

THE HYPOTHETICAL WALL (ASSUME I THROW THE EGG WITH THE SAME INITIAL VELOCITY)

In both cases, the egg has MASS

In both cases, the egg has VELOCITY

So, in both cases the egg has MOMENTUM.

In both cases, the egg CHANGES velocity

So…In both cases, the egg CHANGES momentum

Assuming I throw with the same starting velocity, in both cases the egg experiences the SAME CHANGE in velocity

Therefore, in both cases the egg experiences the SAME CHANGE in momentum

m v = p

m Δv = Δ p or m (v2 – v1) = Δ p

KEEP THIS IN MIND DURING YOUR POGIL TODAY

WallF t

SheetF t

m ΔvΔp

POGIL

• Do NOT use your book… • READ the boxes on the POGIL. Recall prior info,

use your HW, and USE THE BOXES!!!• Check in at stop signs. • You may ONLY USE the computer or a personal

device (iPod, phone, etc.) when the instructions call for it; you may only use the listed site – NOTHING ELSE! Otherwise, computer and group privileges will be revoked for today, and personal devices confiscated.

• Goal is to FINISH THIS TODAY! • Stopping with 20 - 25 minutes left to review a

few key concepts and pass back your tests.

LET’S REVIEW…The following slides contain

some key points you should have learned in today’s POGIL

You will be going BACK to your Do Now in a few minutes to explain what actually happened based on ALL you learned this class and last, so take those out now…

CHANGE in momentum is caused by an IMPULSE

Impulse is a Force exerted for a period of time… it is the PRODUCT of force x time

Since Impulse equals CHANGE in momentum….

IMPULSE = m Δv = Δ p

IMPULSE = force x time

J = F . t or Imp = F . t

J = Δ p or Imp = Δ p

F . t = Δ p or F . t = m Δv

Newton’s 2nd Law is:

Newton’s 2nd Law is:

Substitute the definition for acceleration:

Newton’s 2nd Law is:

Substitute the definition for acceleration:

Rearrange the parentheses

Newton’s 2nd Law is:

Substitute the definition for acceleration:

Rearrange the parentheses

Substitute the symbol p for momentum

Newton’s 2nd Law is:

Substitute the definition for acceleration:

Rearrange the parentheses

Substitute the symbol p for momentum

Move t to the other side of the equation ; impulse equals change in momentum

HERE’S HOW THE UNITS WORK

Since Impulse equals CHANGE in momentum….

So … we can substitute in the units like this:

But remember…the NEWTON is a unit that is shorthand for…

So really, the equation’s units could look like this:

And after cancelling out the ‘s’ in the numerator and denominator:

F . t = m Δv

N . s = kg m s

kg m . s = kg m s2 s

kg m . s = kg m s2 s

BASED ON TODAY’S POGIL….

1. Go back to your Do Now

2. Using ALL key terms you learned (force, stopping time, impulse, change in momentum, mass, change in velocity, etc.) please explain WHY the egg did not break when it hit the sheet:

COMPARING THROWING AT THE SHEET VS.

THE HYPOTHETICAL WALL (ASSUME I THROW THE EGG WITH THE SAME INITIAL VELOCITY)

WALL SHEET

Same Change in Momentum (m Δv)

Same VALUE of impulse (Ft)(*remember, this is the PRODUCT of force x time)

But DIFFERENT forces & stopping times!

WALL SHEET

Ft = m Δv = FtIn both case, the egg experiences the same momentum change and the

same impulse…

But it experiences MORE force in a LESSER TIME when it hits the wall….

And LESS force in MORE TIME when it hits the sheet!

These all have the

same NUMERICAL

VALUE!

IN OTHER WORDS

WallF t

SheetF t

m ΔvΔp

TAKE OUT YOUR HW THAT WAS DUE TODAY- POGIL :

PART 4 – MOMENTUM MATH• Should have finished for HW… any questions?1. 800 kg m/s2. 360 kg m/s If you got 360,000, *check your units!!!*

Use DA to convert 5000g 5 kg first! 3. Zero!!! It is AT REST (if it was not at rest,

you would need to use DA to change pounds kg)

4. Marshmallow: 75 kg m/s Bowling Ball: 40 kg m/s

Mallow wins!*Check your units!!!* Use DA to convert 50g

marshmallow 0.05 kg first!

TONIGHT’S HWRead & Study Ch 7.1-7.2

Complete #7-10 on p. 100

Finish today’s POGIL - don’t forget to check #5-7 online!

We will review the textbook HW #1 - 6 & 7-1 0

We will review the main concepts (NOT all of the answers!) from today’s POGIL (but it is due next class for completion!)

We will complete a series of collision and bouncing demos (Nerf guns, etc.)

We will go over your test that is being passed back today

EXIT SLIP - - please complete HONESTLY & RESPECTFULLY. Please try to correct your tests this evening. You will have an opportunity next class to check, correct, fix any misconceptions, and check in with a teacher to go over your test. Remember, midterm/final questions come WORD FOR WORD from tests & quizzes!

TURN IN YOUR EXIT SLIPS when done BOTH SIDES!

NEXT CLASS

EXIT SLIP