Different types of energy

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There are different forms of energy, but they can generally be divided into two groups: potential and kinetic energy.

A. Potential energy - stored energy and energy of position
- Chemical energy - energy stored in bonds of atoms and molecules
- Gravitational energy - energy stored in an object's height
- Elastic energy - energy stored in objects by tention e.g compressed springs and stretched rubber bands

B. Kinetic energy - motion of waves, molecules, objects, substances, and objects
- Mechanical energy - energy stored in movement of objects
- Thermal energy - vibration and movement of atoms and molecules within substances
- Sound energy - movement of energy through substances in longtitudinal (compression/rarefaction) waves

Reference: http://www.eia.doe.gov/kids/energy.cfm?page=about_forms_of_energy-forms

Cannon... Σ(ﾟДﾟ；

Found a useful simulation for projectile motion~
http://phet.colorado.edu/sims/projectile-motion/projectile-motion_en.html

After a few trials, it is discovered that the launge angle of 45 degree enables the bullet to travel the maximum distance...

Then I found that, the larger the velocity the cannonball has, the longer the distance it can travel...

Some websites said that a longer barrel gives a higher velocity to the cannonball since the long length of the barrel gives a longer distance for the ball to gain acceleration. But for the cannon we are going to make, the cannonball is places at the exit of the cannon so I think this theory may not be useful here...

Newton problems

1. Equilibrium

Assumption:
-Positive axes
-∑F = 0 ( ∑Fx = 0 , ∑Fy = 0), a = 0
- no friction
- no air resistance
- rope is weightless

When calculating, divide all the force to x-axis and y-axis,
Fx = max        Fy = may
Fx = 0              Fy = 0



2. Inclines

(a) object is at rest
Assumptions:
- postive is along the incline direction
- ∑F = 0, a = 0
- no air resistance
- FN is perpendicular to incline
                     ∑F = ma 
∑Fx = max                ∑F = may
∑Fx = 0                       ∑F = 0
Fgx - f = 0                 FN - Fgy = 0




(b) object is moving
Assupmtions:
- positive is along the incline direction
- ∑Fy = 0 , ∑F is not equal to 0
- no air resistance
- FN is perpendicular to incline
use the same method of calculation as when object is at rest

3. Polley

Assumptions:
- polley is frictionless
- rope is frictionless and weightless
- no air resistance
- 2 systems (2 FBDs)
- T1 = T2
- a of the system is the same (ay1 = ay2)

Note that ∑Fx = 0 for both objects
Do the calculation by dividing the foerces into x and y.


4. Train

Assumptions:
- Use 3FBDs  to find T
- no air resistance
- ay = 0
- cables are weightless
- positive is in the direction of a
- a is consistant

Assume the whole system as an object to calculate the acceleration
Then use 3 FBDs to find tension amoung the masses


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