ENGR Mechanics: Statics: HW#1 & Conversion of Units

The Gimli Glider Incident:
July 23, 1983, Air Canada Flight 143 ran completely out of fuel halfway through its flight from Montreal to Edmonton because the amount of fuel needed was incorrectly calculated.

1.77 pounds/liter???

0.8 kg/liter???

http://www.pri.org/stories/2012-02-23/new-clues-emerge-centuries-old-swedish-shipwreck

"Vasa set sail on her maiden voyage on August 10, 1628. At the time, she was the most powerfully armed warship in the world, with 64 bronze cannons.Twenty minutes into her journey, the ship was hit by two strong winds. It heeled to port, water gushed in, and the ship sank less than a mile into the journey. Thirty people died.
"We have, over the last three years, measured every single piece of the wood in the ship," says Hocker. "If we want to understand how the ship was built, that's what it takes."
Hocker's meticulous measurements paid off. They gave him fresh insight into what made the Vasa unstable.
For one thing, the ship was asymmetrical, more so than most ships of the day.

Why was the ship so lopsided?
While examining the ship, Hocker discovered four rulers the workmen had used. Those rulers were based on different standards of measurement at the time.
Two were in Swedish feet, which were divided into twelve inches. The other two were in Amsterdam feet, which had eleven inches in a foot. So each carpenter had used his own system of measurement.
"When somebody tells him, make that thing four inches thick, his four inches is not going to be the same as the next guy's four inches," says Hocker. "And you can see those variations in the timbers, as well."

What are units?
Conventions used for describing the magnitude of physical quantities.

What are Equations?
Formulas relating different physical quantities (or units) to one another.

Most equations are nothing more than unit conversion statements....

Tip:
If the units work out correctly in your calculations, you're more than half way there.

Some unit conversion tables:

Unit conversion class exercise:
Without using any electronic devices, estimate the properties of mystery items from the grab bag in English and SI units.

Intuition vs. Math
What length, time, and mass scales are intuitive?
What scales follow classical Newtonian Physics?
At what scale does classical physics break down?

What can you perceive without tools of any kind - with just your bare senses?

Mass__________________________

from Greek μᾶζα (maza), meaning "barley cake, lump [of dough]" The property of a physical body which determines the body's resistance to being accelerated by a force and the strength of its mutual gravitational attraction with other bodies.

What is the largest object you can lift?

Aug 8, 2012 Behdad Salimikordasiabi, 22, won the gold medal in the men’s super-heavyweight division of weight lifting, cementing his status as the biggest sports hero in Iran. Salimikordasiabi holds the world record in the snatch at 472 pounds (214 kg = 214,000 g).

What is the smallest mass you can detect?

One drop of water -
50 ul - 99 ul
60 ul = 0.06 grams = .0001 lbs
(one liter of water weighs a kilogram)

What is the order of magnitude of masses we are used to dealing with?

Length_______________________
Standing in one place, using only your eyes

How far can you see?
http://www.livescience.com/33895-human-eye.html
Andromeda galaxy - 2.6 million light years from earth...
2 miles (3.22 km) away - when you start seeing headlights on a car.

What is the smallest thing you can see?
Dust in the air :
10-1000 microns = .0004 - .04 inches

After contemplating what scales humans usually operate in.... now contemplate

What scales does the universe act on?

Mass of an electron = 9.10938291 × 10^-31 kg

Plank Length = 1.616 × 10^-35 m

The speed of light = 299,792,458 meters per second = 186,000 miles/sec

Size of the universe ~ 14 billion light years

Density of observable universe ~ 3 × 10^-30 g/cc

Mass of observable universe ~ 3 × 10⁵⁵ grams

Some scales are not intuitive, and can only be partially perceived through the use of math and tools.

Puzzles of modern science:
The laws that govern the universe on the largest scale are entirely different from the ones that govern on the medium and smallest scales.

General relativity:
Applies within the largest scales

Unified description of gravity as a geometric property of space and time, or spacetime.

curvature of spacetime → →
→→energy & momentum of matter and radiation

(Predictions of general relativity differ significantly from those of classical physics, especially concerning the passage of time, the geometry of space, the motion of bodies in free fall, and the propagation of light.)

Classical Physics:
Applies within medium scales & the rules we will be using within our statics class.

Quantum mechanics:
Applies within small nanoscopic scales, or atomic and subatomic length scales.

particle physics, nuclear physics, quantum optics...
wave-particle duality, principle of uncertainty

entanglement - "spooky action at a distance", etc.

Start thinking about the units around you....

Current Gasoline prices:
http://www.mytravelcost.com/Norway/gas-prices/
http://www.mytravelcost.com/petrol-prices/

Group exercise - Look up the current Euro→$ exchange rates, and use conversion equations to fill in the below table:

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Set up a unit conversion excel worksheet for use throughout the rest of the semester:

* check your email
* open the attachment
* Notice the equations & "CONVERT" functions that are typed into some of the cells.

* change any of the "1.00"'s to another #, and watch what happens.