Lesson Strategy- Impulse and Momentum

7/27/2019 Lesson Strategy- Impulse and Momentum

1/30


2/30

Review that:

Bodies at rest will remain at rest

while bodies in motion will

continue to move at a constantvelocity unless a net force is

acted upon them(First Law: Law of Inertia)


3/30

Review that:

Inertia is the tendency of the

body to retain its state of motion

(either at rest or in motion)


4/30

Review that:

Mass is the quantitative measure

of the objects inertia. The

greater is its mass, the greater isits inertia.


5/30

Review that:

The acceleration of an object is

directly proportional to the Net

Force applied on it and inverselyproportional to its mass

(Second Law: Law of Acceleration)


6/30

Review that:

Acceleration is the objects

change in velocity over a certain

period of time


7/30


8/30

Case 1:

Two balls (tennis and bowling balls)

are rolling with the same velocity on

a smooth floor. Which between themis much easier to stop?


9/30

Time = 0 seconds


10/30

2 seconds later


11/30

Case 2

A soccer ball which is initially at

rest experiences a change in

velocity to 5m/s


12/30

How would you describe the

motion of the ball?


13/30

What would have caused the ball

to accelerate?


14/30

How quick are your eyes? Identify velocity, force, mass and time.


15/30

Its time to share

what you observed!


16/30

Analyze and solve:

A 25,000 kg bus from Tuguegarao

moves at 25 m/s to Ilagan. What

is the momentum of the bus?Assume that the velocity of the

bus is constant.


17/30

Analyze and solve:

John hits a 0.05 kg ball, going at a

speed of 65m/s. What is the

impulse to the ball?


18/30

Analyze and solve:

Automobile companies often test the

safety of cars by putting them through

crash tests to observe the safety of thepassenger compartment. If an 1100 kg

car is sent towards a cement wall with a

speed of 15 m/s and the impact stops thecar in 0.09s, with what average force is it

brought to a stop?


19/30

Associate yourmathematical

relationship

Ft = mvwith this:


20/30

Associate your mathematical relationship Ft = mv


21/30

Associate your mathematical relationship

Ft = mv


22/30

Catching Raw Eggs


23/30

Apply what you learned:

If you are catching a fast baseball

with your bare hand, you extend

your hand forward so youll haveplenty of room to let your hand

move backward, extending the time

of impact and thus reducing theforce of impact.


24/30

Apply what you learned:

A person jumping from an elevated

position bends his knees upon

making contact (thereby extendingthe time during which his

momentum is being reduced by 10

to 20 times that of a stiff-leggedabrupt landing.


25/30

Test your understanding:

Interpret the situation

illustrated on the next

slide!


26/30


27/30

Question 1:

If the boxer is able to make the

duration of impact three times as

long by riding with the punch, byhow much will the force of

impact be reduced?


28/30

Question 2:

If the boxer instead moves into

the punch as to decrease the

duration of impact by half, byhow much will the force of

impact be increased?


29/30

Assignment:

Follow-up assignment:

Explain how the concept of impulse and

momentum is applied when the karate expert

fracture a stack of bricks with the blow of his barehands.

Advanced assignment:

How is momentum conserved?

Differentiate elastic from inelastic collision.


30/30

Picture credit to Jericho Torres, IV-Alpha 2010-11.

Domo arigatou

gozaimasu!Thank you very much!

Lesson Strategy- Impulse and Momentum

Documents

Transcript of Lesson Strategy- Impulse and Momentum