Energy, Work, Power

Energy - ability a physical system has to do work on other physical systems

Work - transfer of energy - force acted over a distance (W = f * d)

ΔE = W
...since energy is conserved, the transfer of energy is equal to the initial energy.


However, energy can be transformed to other types
ΔE = W + Q, Q standing for heat

The major difference between energy and work is that energy is the capability to do work while work is the result of the conversion of energy. Without energy, there is no work but there could energy without work being performed. However, these terms could be used interchangeably since  ΔE = W when no energy is lost.

Power - the rate at which work is done or energy is converted

Cannon

What is a cannon?

A cannon is any piece of artillery that uses an explosive-based propellant to launch a projectile.

Principle behind the cannon?

A charge is loaded into the cannon (e.g. gunpowder) and the projectile (usually a cannonball) which wishes to be propelled, is deposited into the cannon on top of the charge. Wadding (something used to contain the charge) is then placed onto the cannon along with the fuse. The fuse is lit (usually with fire) and the charge ignites. The gases from the charge expand and generates pressure within the confines of the cannon. As a result, the projectile flies out (if the pressure inside is greater than the projectile's mass, the friction acting on the projectile, and the gravity acting upon it).

Essential parts of a cannon

(1) The projectile

(2) The charge

(3) Vent/ touch hole (the fuse/ ignition device) 

Dynamics Lab Results

Hmmm.. did I do this right? O__O

(PS. Why is ticker tape so hard to use D:)

Paper Structure

Today, we made a free-standing paper structure out of some scotch tape and 3 sheets of newspaper.

193 cm tall 

We made a base similar to a tripod, except the middle part also touches the ground. We focused the center of gravity at the base and luckily, the base was enough to withstand the weight of the entire structure. However, the top of our structure was bending a slight bit. 

Unfortunately, our structure was off by 10 centimeters from the winning group. We should have saved some tape and stuck it at the top. Lol.

Tall Structures

An example of an extremely tall structure is the....

CN TOWER!!

The CN Tower was the world's tallest free-standing structure from 1975-2007. 

Currently, the world's tallest building is the Burj Khalifa in Dubai

So how were these towers and buildings built so tall without tipping over?

(1) Low center of gravity (near the ground)

(2) Shape of a triangle/ pyramid/ cone (where the weight it mostly at the bottom, little weight at the top)

(3) Wider the base, the more stable the structure

(4) Have holes in the structure where it isn't necessary to cover (acting like arches) - reduces weight but carries same amount of mass

(5) Structure's base is flat - therefore balanced base

(6) Strong support/ beams, etc.

Projectile Motion

The 5 graphs below show the 5 cases of projectile motion.

(1) The object is thrown downwards to the ground

(2) The object is throw upwards to higher elevation and gets caught

(3) The object is thrown into the air from the ground and eventually falls back down to the ground, further away from where the object originally stood

(4) The object is thrown from the ground, reaches the peak, and falls down slightly, getting caught in mid-air

(5) The object is thrown up from mid-air and falls to the ground

And below are the projectile motion questions....

Aerodynamics

Principles:
- A glider moves through the air without the help of a motor or engine
- A glider can move through air and descend gently

Facts:
- Design of wing and glider body has a major contribution to how it glides in the air
- Adding some weight to parts of glider will help it stay up in the air, have lift, and travel in a straight path (rather than spinning or nosediving)

This is a basic glider (paper airplane)

So how does it fly??

In flight, the glider has three forces acting on it (compared to the four forces that act on a powered aircraft). Lift, drag, and weight (since there is no engine for there to be thrust).

In order for the glider to fly, it must generate lift to oppose its weight. To generate a lift, a glider must move through the air. However, there is no thrust to oppose the drag as the glider moves through the air, therefore a glider quickly slows down until it can no longer generate enough lift to oppose its weight.

Even though a glider does not have thrust during flight, it has an initial velocity (coming from the person exerting force upon the glider [throwing the aircraft]). That's where the velocity needed to drive the aircraft comes from.

For a glider to remain up in the sky for a long time, it must be efficient and pass over any nearby updrafts (rising air).