• Support PF! Buy your school textbooks, materials and every day products Here!

Differential Equations KE Problem

  • Thread starter steven452
  • Start date
  • #1
3
0

Homework Statement



We're supposed to find the object's KE and heat. Given:

Forces on Object: Air Drag + Gravity
Air Drag = .5(coefficient of drag)(1.2 kg/m3)v2A
A = cross sectional area
R = Radius of object
Object is X Km above the ground
Initial velocity = V

We are told it should be an initial value problem.

Homework Equations



Possibly y"+ (Force due to Drag)y' + (gravity)y = 0

The Attempt at a Solution



I tried plugging in the initial conditions to the equation above, but I'm stuck at that point.
 

Answers and Replies

  • #2
283
0
Possibly y"+ (Force due to Drag)y' + (gravity)y = 0
How did you get that equation?

Since kinetic energy has nothing to do (directly) with position, you shouldn't have to solve for y (which I'm assuming stands for the height of the object); instead, focus on v(t), and don't forget that a(t) = dv/dt
 
  • #3
3
0
I just sort of assumed that's the equation we had to use, but I wasn't sure?

What initial value differential equation should I be using?
 
  • #4
283
0
You should be able to derive an equation using newton's second law and what you know about the forces acting on the object
 
  • #5
3
0
I was originally going to do it entirely with Newton's laws, but I'm having a hard time seeing how Newton's equations can "convert" into DE?
 

Related Threads for: Differential Equations KE Problem

  • Last Post
Replies
4
Views
3K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
4
Views
2K
  • Last Post
Replies
3
Views
3K
  • Last Post
Replies
1
Views
12K
  • Last Post
Replies
4
Views
2K
  • Last Post
Replies
1
Views
5K
Top