Upcoming Deadlines

Fourth Homework (Analyzing Video)Due Thursday, Sept. 15th (This week)15 points (10 points if late)

Fifth Homework (Path of Action Analysis)Due Thursday, Sept. 29th (Two weeks)15 points (10 points if late)

For full schedule, visit course website:ArtPhysics123.pbworks.com

Pick up a clicker, find the right channel, and enter Student ID

Homework Assignment #4We will be using a video analysis program called

"Tracker" to study motion. Download a copy of the program from the Tracker website:

http://www.cabrillo.edu/~dbrown/tracker/

Run the Tracker program on your computer, import the video clip of a falling object that you created in the previous homework assignment and analyze the falling motion.

This assignment is due by 8am on Thursday, September 15th (this week).

Homework #4

HorizontalMotion

VerticalMotion

Image you post on your blog should look something like this.

Activating your Clicker

* Turn on your clicker.* Enter the channel number or letter for

joining this class. Hit Enter/Send key.* Clicker should read AP123KF11* Type in your student ID; hit Enter/Send.Clicker is now ready to use; leave it on.

Hit any key to wake the clicker from sleep mode.

Survey Question

How easy have you found it to use the Tracker software?

A) Pretty easy to useB) A little confusing but OKC) Frustrating to useD)Haven’t tried using it yet

Note: You score 1 point of credit for answering survey questions, regardless of your answer.

Review QuestionWhat’s wrong with the spacings in these drawings of a ball thrown in the air?

A) Vertical spacings wrong; horizontal spacings are OK.

B) Horizontal spacings wrong; vertical spacings are OK

C) Both vertical and horizontal spacings are wrong.

D) Actually, the spacings are OK for this path of action.

Review Question

C) Both vertical and horizontalspacings are wrong.

The vertical spacings are too uniform; the motion should slow in as it rises.

The horizontal spacings should be uniform but instead they slow out going left to right.

Madagascar 2 (2008)Carefully observe the path of action when the plane is in the air.

http://www.youtube.com/watch?v=Anflb_oWdgo

Review Question

This path of action is a parabolic arc.

Trueor

False

Review Question

False.The arc is shallow when the plane flies off the cliff but very steep after the apex.

Parabolic arc is symmetric about the apex

Paths ofAction(cont.)

Throwing at an Angle

With no gravity, a thrown object would follow a straight line.

Due to gravity, the object falls beneath this line, just as if released from rest.

No Gra

vity

WithGravity

12Frames

4 feet

16 feet

36 feet

24Frames

36Frames

“Shoot the Monkey”

Monkey lets go of the branch the moment he hears the gun fire.

Rifle is aimed at monkey’s nose.

Bullet hits the monkey:A)Above the noseB)On the noseC)Below the nose

“Shoot the Monkey”

B) On the nose.Bullet and monkey fall at same rate so they stay at the same height.

This happens even if the gun aims at an angle.Bullet and monkey fall at same rate.

“Shoot the Monkey”

http://www.youtube.com/watch?v=cxvsHNRXLjw

Speed (1994)In Speed, a city bus jumps across an unfinished freeway bridge in Los Angeles.

Is this jumpunrealistic?

Speed (1994)

http://www.youtube.com/watch?v=CX6aVa7B2qQ

Speed (1994)

The bus should be in the air for about one second (although in the movie it’s over seven seconds).

Missing section is about two bus lengths, which is 80-90 feet. At 65 m.p.h. you travel about 95 feet per second.

Speed (1994)Since the bus is in the air for about a second it drops 16 feet so the angle of the bridge would have to be about 10 degrees for the bus to land correctly on the other side.

90 feet

16 feet

Popping a wheelie does not help!

Speed (1994)The film makers did not jump a bus over a gap in a bridge. In fact the gap in this bridge is fake; it was painted in digitally.

However they forgot to paint out the shadow on the ground.

Speed (1994)

This part of the film was digitally painted in.

The bus jump is a stunt filmed with a real bus but the gap is fake.

Speed (1994)

http://www.youtube.com/watch?v=CX6aVa7B2qQ

Maximum RangeMaximum range is at a launch angle of 45

degrees (when air resistance is negligible).

Range

Heig

ht Same initial speeds

Trebuchet

Siege of Jerusalem

The trebuchet was the ultimate mechanical siege engine.

Developed in the Far East and brought west in the 10th century by the Mongol and Muslim armies.

European armies adopted the trebuchet during the Crusades of the 12th century. Counterweight lifted by human powered “hamster wheels”

MangonelThe mangonel is a simplified

trebuchet using a fixed counter-weight.

Releasing the ProjectileThe release

mechanism is designed to throw the rock at a 45 degree angle.

45º

Release

Importance of RangeHeavy medieval weapons had to operate outside the range of archers (about 200 yards).

A trebuchet can hurl stones out to 350 yards, with a launch speed of 130 miles per hour.

LotR: Return of the King (2003)

http://www.youtube.com/watch?v=7bFTw95pJp8

Kingdom of Heaven (2005)

Several full-size trebuchets were built for the film “Kingdom of Heaven.”Many more were inserted into the movie by digital effects.

Tracking and Motion Graphs

Using Reference

Animator Ken Harris at work, using himself as a model.

Visual artists have always used models and reference in their work.

One of the most useful tools for the modern animator is the digital movie camera.

Video Reference & Madagascar 2

http://www.youtube.com/watch?v=GUBEwUvtssE

Horton Hears a Who

http://www.youtube.com/watch?v=ouaspd_dr5o

Tracking and Motion Graphs

Next Lecture

Analyzing Video (Tracker) due Thursday, 9/15 @ 8 AM