Do Now

• Turn in #11-13• Take out #1-10 (page 100); we are popcorning

them• YOUR RESPONSIBILITY TO… – listen, – ask questions, – make corrections,– Get the help you need!

• Rank these cars based on momentum before they hit the brakes:

• Remember…. m v = p

20,000 kg m s

10,000 kg m s

10,000 kg m s

10,000 kg m s

20,000 kg m s

5,000 kg m s

F B = C = D A = E

Most NEGATIVE Most POSITIVE

Look at Car A…m = 1000 kgv = 20 m/s

Solve for “p” using mv = p

mv = (1000kg)(20 m/s)mv = 20,000 kg m s

• Rank these cars based on THE IMPULSE needed to stop them

• Remember…. Ft = m v Δ

- 20,000 N.s -10,000 N.s -10,000 N.s

-10,000 N.s -20,000 N.s -5,000 N.s

A = E B = C = D F

Most NEGATIVE Most POSITIVE

Look at Car A…m = 1000 kg

vΔ = v2 – v1

vΔ = 0 – 20 m/sv = - 20 m/sΔ

m vΔ = (1000kg)(-20 m/s)m vΔ = -20,000 kg m sIn other words…

-20,000 N s

• Rank these cars based on THE FORCE needed to stop them

• Remember…. Ft = m v Δ

Not enough info to solve!

Most NEGATIVE Most POSITIVE

Look at Car A…

m vΔ = Ft -20,000 kg m = Ft s

Slight problem….We don’t know the stopping time!

Without ‘t’ we can’t solve for F!

• Take out the POGIL that looks like this:

• We are checking the LAST PAGE

WHAT? HOW? LIST SOME EXAMPLES?

CASE 1

Increase Momentum(usually means velocity increases)

Apply the greatest force for the longest time

CASE 2

Decrease Momentum(usually means velocity decreases)

Minimize forces by increasing stopping time

Maximize forces while decreasing stopping time

FOLLOW THROUGH in sports

Bending knees when jumpingBungee jumping with elasticRunning on asphalt Airbags!

Head 1st into brick wall Bungee jumping with rope

Run on concrete

Pulling slingshot back all the way

Moving hand back when catching

Moving INTO a punch Karate chop

Locked knees when jumping

Your responsibility to…

• Check• Correct• Understand WHY the answer it what it is• Check in with a peer or teacher for help if

needed

• Force x time = Impulse = mass x change in v= Momentum Change

There are 2 types of algebra problems, combined into one table.

Here are your hints when solving:

• The 3rd and 4th columns are always equal; that is, the impulse is always equal to the momentum change.

• If any two of the first three columns are known, then the remaining column can be computed.

• This is true because the impulse=force • time.

• Knowing any two of the last three columns allows us to compute the remaining column.

• This is true since momentum change = mass • velocity change.

FIRST ROW - - Do we have enough info to solve for IMPULSE?

NO – we only know time, not force!

Do we have enough info to solve for change in momentum?

YES! We have mass, and change in velocity!

Change in Momentum = mass x change in vel.

Change in Momentum = 10 kg x (-4 m/s)

Change in Momentum = - 40 kg m/s

Force x time = Impulse = Change in Momentum = mass x change in vel.

- 40 kg m/s

Do we have enough info to solve for IMPULSE?

YES! It equals momentum change!

Impulse = - 40 Ns

Do we have enough info to solve for force?

YES! Force x time = Impulse

Force x (0.01s) = - 40 Ns

Force = - 4000 N

Force x time = Impulse = Change in Momentum = mass x change in vel.

- 40 kg m/s- 40 Ns- 4000 N

2ND ROW - - Do we have enough info to solve for FORCE?

YES! Force x time = Impulse

Force x (0.1s) = - 40 Ns

Force = - 400 N

Do we have enough info to solve for momentum change?

YES! Impulse = change in momentum!

Do we have enough info to solve for change in velocity?

YES! Change in Momentum = mass x change in vel.

-40 kg m/s = 10 kg x change in vel.

Force x time = Impulse = Change in Momentum = mass x change in vel.

- 40 kg m/s- 40 Ns- 4000 N

- 400 N - 40 kg m/s - 4 m/s

Force x time = Impulse = Change in Momentum = mass x change in vel.

- 40 kg m/s- 40 Ns- 4000 N

- 400 N - 40 kg m/s - 4 m/s

- 200 - 4- 20,000

25-2000.01

-200 -200 -4

Solutions are above…

Exit• Check your chart

HW FOR TONIGHTFinish the HW Worksheet you will get on your way out the door.

Finish PAGE 2 of today’s POGIL…we will finish the rest of it next class

QUEST Jan 23rd (date TBD)**Since it is an OPEN NOTES QUEST, no study guide or formulas provided.However, study as if it were CLOSED NOTE!!!