Upcoming Classes

Tuesday, Oct. 9th

Dissecting the iPodAssignment due:

* Homework #4 (Egg container)

Thursday, Oct. 11th

Design at the Nexus

Assignment due:

* Topic and outline for second paper or oral presentation

Upcoming Deadlines

Thursday, October 11th

Outline of second oral presentation or written paper

Tuesday, November 6th

Second Set of Oral Presentations

Second term paper (if not presenting)

Oral Presentations (II)

The following persons will give oral presentations on Tuesday, November 6th :

• Luttrell,Katherine• Macdonald,Keith• McDonald,Kathleen• Mendoza,Jazmin• Nguyen,Jennifer• Nguyen,LindaFor everyone else, term paper is due on that date.

Extra Credit: SF Museum of Art

Visit San Francisco Museum of Modern Art and see Abstract Expressionist paintings.

Turn in your ticket receipt ($7 for students). Worth one homework assignment; deadline is Oct. 16th

Guardians of the Secret, Jackson Pollock, 1943

Extra Credit: San Jose Ballet

See a performance of San Jose Ballet in San Jose Center for Performing Arts (Nov. 15th – 18th ).

Turn in your ticket receipt. Worth one homework assignment or three quiz/participation credits.

Ramon Moreno in CARMINA BURANA

The Two Forcesof the Universe

Two Fundamental Forces

There are two fundamental forces in the universe:

• Gravitational force

• Electrical force

All other forces are actually a result of one of these two fundamental forces.

Non-fundamental Forces

Contact forcesbetween materials are due to electrical forces between molecules

Chemical reactions, such as burning, also due by electrical forces between molecules

Weather due to buoyant motion of air (gravity) and solar radiation (electromagnetic)

All familiar forces, such friction and pressure, are due to the two fundamental forces

Newton and the Moon

Newton realized that Earth’s gravity was the centripetal force that kept the moon in orbit.

Also discovered that gravity was weaker at that great distance.

Gravityforce

That a force could act at a distance was a revolutionary concept

Gravity & Distance

We don’t notice that gravity gets weaker as we move away from Earth because we rarely go very far.

Moon is 30 Earth

diameters away

Area & Distance

These four figures are equally spaced indistance and, in perspective,you are standing that distance from the first.

At twice the distance,the face is ¼ the size.

At four times the distance face is 16th the size.

Demo: Perspective Cards

Hold large card at arm’s length.

Close one eye then hold small card at a distance such that it is same size as large card.

That distance will be half way between your eye and large card.

1

1 2

3 4

Arm’s length

Half

Inverse Square Law

Gravity force weakens with distance as the inverse of the square of the distance.

Geometric property of area and distance. Outer circle is twice Earth’s radius

so it has 4 times the area

Earth Gravity

1/4 Earth Gravity

Universal Law of Gravity

Force of gravity has magnitude given by

(Gravity Force) = (G) x

ObjectA

ObjectB

( Mass of Object A ) x ( Mass of Object B)

( Distance ) x ( Distance )

DISTANCE

Force Force

Equal and opposite forces(Newton’s Third law)

Universal Gravity Constant, G

In the formula for gravity force, we have

G = 0.0000000000667 N m2 / kg2

= 6.67 x 10–11 N m2 / kg2

The formula and the constant are called “universal” because, up to now, this theory predicts gravity anywhere in the universe.

Cavendish Experiment

For non-astronomical objects gravity force is very small.

Need sensitive balance to detect.

First measured by Cavendish in his home laboratory in 1797 at age 67.

Salvador Dalí

Salvador Dalí, (1904-1989) was a flamboyant Catalan-Spanish painter who popularized Surrealism.

Dalí had a life-long interest in science, which influenced many of his compositions.

Dalí & Special Relativity

The Persistence of Memory (1931)

Time is not absolute but instead is relative to motion by the universality of electromagnetic radiation (i.e., the speed of light), as shown by Einstein in his theory of special relativity published in 1905.

Dalí & Quantum Mechanics

The Disintegration of the Persistence of Memory, 1952–1954

In his "Anti-Matter Manifesto“ (1958), Dalí wrote,

Werner Heisenberg (1901-1976) introduced the uncertainty principle of quantum mechanics, which states that there are fundamental limits on what can be known. Heisenberg won the Nobel prize in Physics at the age of 31.

In the Surrealist period I wanted to create the iconography of the interior world and the world of the marvelous, of my father (Sigmund) Freud.

Today the exterior world and that of physics, has transcended the one of psychology. My father today is Dr. (Werner) Heisenberg.

Dalí & Gravity

Dream Caused by the Flight of a Bumblebee around a Pomegranate a Second Before Awakening (1944)

Gravity is distorted or absent in many of Dali’s paintings

Dalí & Gravity

Dalí Atomicus, photo by Philippe Halsman in collaboration with Salvador Dalí, 1948

Making of Dalí Atomicus

On the count of three, his assistants threw three cats and a bucket of water into the air; and on the count of four, Dalí jumped and Halsman snapped the picture.

While his assistants mopped the floor and consoled the cats, Halsman went to the darkroom, developed the film, and reemerged to do it again.

“Six hours and twenty-eight throws later, the result satisfied my striving for perfection,” wrote Halsman in his book Halsman on the Creation of Photographic Ideas. “My assistants and I were wet, dirty, and near complete exhaustion—only the cats still looked like new.”

Dalí and Halsman were mesmerized by the idea of suspension captured in a photograph. They argued back and forth on aspects of the composition, such as blowing up a chicken and whether to use milk or water. In his New York studio, Halsman suspended an easel, two paintings by Dalí (one of which was “Leda Atomica”), and a stepping stool while having his wife, Yvonne, hold a chair in the air.

Freefall & WeightlessnessFreefall is a state of weightlessness, even though gravity is present.

Movie: Roller Coaster

NASA’s “Vomit Comet”

NASA has a special airplane for training astronauts in free-fall weightless conditions.

The “Vomit Comet” nickname tells you it’s quite a wild roller-coaster ride. The plane flies between 20,000 and

30,000 feet, same as commercial flights.

Pow

erC

limb

WeightlessFreefall

Pull out

of Dive

Flight of the “Vomit Comet”

At the top of the arc, the plane’s trajectory is projectile motion.

Boeing 707 (modified)

Einstein’s General Relativity

General relativity, published by Einstein in 1915, unifies special relativity and Newton's law of universal gravitation.

In this theory gravitation is due to the curvature of space-time produced by the mass-energy.

Einstein’s Argument

Imagine a box on Earth and one in space

Motion of objects looks the same whether or not the acceleration is due to gravity.

Equivalence Principle

Push

Because light travels with constant speed, in the accelerating box light is deflected.

Einstein’s Argument

Push

In the time that it takes the light beam to cross the length of the box, the box has moved upward some distance.

Appears as if the light is deflected downward

Einstein’s Argument

Push

Distance the box travels

upward

Light Deflected by Gravity

Even though it has no mass, light is deflected by gravity, which has been astronomically confirmed.

By Equivalence Principle

Electric Charges and Forces

There are two types of charge:

positive charges and negative charges

REPEL REPEL ATTRACT

Like charges repel, opposite charges attract.

Electrons, Protons, & Atoms

Helium atom

Electrons

Protons

Electrons carry negative charge.

Protons carry positive charge.

Electrons are loosely bound to atoms

Protons are tightly locked

within the nucleus.

Objects are usually neutral but can easily acquire or lose electrons to become charged.

Charging by Friction/Contact

Electrons move easily so an object can become charged by rubbing electrons off the object’s surface.

• Brush your hair with a plastic comb.

• Walk across a carpet with plastic-soled shoes.

Electrons taken off of fur onto rubber rod

Demo: Dial Electroscope

Alternative design for electroscope

Charged

Neutral

Demo: Van de Graff Generator

Van de Graff deposits large quantities of excess charge on its globe.

A person with long hair can become a human electroscope.

Conductors & Insulators

Materials, such as metals, in which electrons flow freely are called electrical conductors.

Materials, such as plastic and wood, in which electrons do not move easily are called electrical insulators.

Materials, such as silicon, that can act as conductors or insulators under different conditions are called semiconductors.

Plastic Insulators

Plastic insulation on step of van de Graff and charge wand keep charge from leaving the metal balls.

Plastic insulation on wire prevents charge to leave wire except at the ends, where the conducting metal is exposed.

Demo: Tesla Coil

Air is an insulator but at high voltages it can conduct electricity as lightning.

PortableTesla coil

Tesla Coils

Very high voltages achieved by large Tesla coils.

Homemade, backyard model Fry’s Superstore, Fremont CA

Coulomb’s Law

Electric force has magnitude given by

(Electric Force) = (k) x

ObjectA

ObjectB

( Charge of Object A ) x ( Charge of Object B)

( Distance ) x ( Distance )

DISTANCE

Force Force

Equal and opposite forces(Newton’s Third law)

Demo: Induce the CanCharges separate in the can. Force of attraction is

stronger since opposite charges are closer.

MetalCan

(Neutral)

Charged

Object

++

+++

+

AttractionForce

RepulsionForce

Can Rolls

Demo: Electroscope & Induction

The legs of the electroscope separate when charged rod brought near the electroscope.

Charge induction pushes electrons into the legs. “Legs”

Negatively charged rod repels electrons so they move as far away as possible.

++

++

+

+

Lightning Storms

Charge separates inside of thunderclouds.

The lower part of the cloud is negatively charged.

This induces a positive charge on the ground.

When the voltage difference is high enough, a lightning bolt can occur.

Charge Polarization

Charge polarization occurs when the positions of the electrons and protons in an atom are skewed.

Neutral Polarized

ChargedRod

PolarizedAtoms

Demo: Static “Cling”

Charged object attracts a neutral insulator by inducing charge polarization in the neutral object.

ChargedBalloon

NeutralWall

Po

lari

zatio

n

Polarization

ChargedComb Neutral

Paper

More important than static electricity is electric current, when charges move.

Next lecture we’ll see how everything in this store works

Electric Current

The Third Force

Gravitational and electrical force are the two forces we regularly experience but there’s actually third universal force in nature:

The Sun, photographed from space Explosion of an atomic bomb

the nuclear force

Next Lecture Dissecting the iPod

Remember:Assignment due: Homework #4

Egg package design & prototype