Physics Simulations

1
Physics Simulations

• In this lab class we will be creating Simulations
  of Gravitational Systems. This will involve
  several steps
• Analysis of Problem
• Design of Appropriate Classes
• Member Variables
• Constructors
• Methods
• etc.
• Code should be reusable
• Testing Code

2
Previous Work

• Assume understood and completed 281
• Need to be able create classes
• Graphics
• Mathematical Calculations

3
Grading

• 100 Course Work
• divided into 5 weekly projects and final report
  on project.
• Will need to document all code.
• Please back up all of your code onto floppy disks

4
Course Outline

• Week 1
• Class Design ThreeVector Class
• Class Design of MassiveObject Class
• Class Design of GravitationalForceField
• Create ThreeVector Class with following
  properties
• dotProduct
• set
• add
• subtract
• cross product
• print
• get
• magnitude
• scalar multiplication

5
Course Outline

• Week 2
• Physics Simulation issues
• Simulate Massive Object on Earths Surface in 2d
• Week 3
• Simulation of 2D orbiting bodies
• Simulation of object in tunnel through center of
  earth
• Week 4
• Simulate 3 bodies in 3D
• simulate N bodies in 3D
• Week 5 Flashy Graphics..

6
Gravitation

• Force on a massive object depends on all the
  massive objects in the system.
• What properties does a Gravitational Object have?

7
Potential and Force

• Given a Potential Field G(x,y,z) the force is
  given by the three dimensional vector derivative
• Requires mathematical calculation of the
  derivatives of a function
• We can create a force field class instead.

8
Class Design

• Class Design ThreeVector Class
• Class Design of MassiveObject Class
• Class Design of GravitationalForceField
• Work together on what are the properties
  required.
• Will need to write up your design in your log
  book.

9
Implementation of Vector Class

• Member Variables should be private
• allows you to change implementation without
  changing user code
• Access all variables via public methods
• Document your code.
• Write a class to test your code
• What are appropriate tests?

10
Example of Documented Code
/ An example of documented code _at_author
Iain Bertram _at_version 1.0 / public class
Sample private double myVariable /
The Default Constructor, set to zero
/ public Sample() this.myVariable
0.0 / Constructor that sets a
value / public Sample(double
setValue) this.myVariable setValue
11
Continued
/ Method to obtain the value stored in
the class / public double getVariable()double
argthis.myVariable return arg /
Method to set variable / public void
setVariable(double setValue) this.myVariable
setValue / Method to print Variable
/ public void print() System.out.print("The
variable is "this.myVariable"\n")