Darshiva8

I love smart women!!! O +1

Congratulations! ************** For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return. ~Leonardo da Vinci~

Quick thread diversion.... I'm glad you liked the skydiving simulator! The company I work for developed it. I didn't know they were going to have a set up in Florida until last week. I'm so happy it had a good reception!

Oh, and your initial vector, y0, in your main file is [0 85 (convert to proper units) 0 0] ************** For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return. ~Leonardo da Vinci~

Alrighty, try this. It's assuming all sorts of things about the drag coefficient, but we'll just assume it's constant all the way through. I doubt your professor is going to care about such vaguaries. Anyway, here's the derivation: p=xi+zk (p is your position vector, i and k are unit vectors) dp/dt=dx/dti+dz/dtk (velocity vector) d(dp/dt)dt=d(dx/dt)/dti+d(dz/dt)/dtk (acceleration vector) Now let's look at Newton's 2nd Law, F=ma a is your acceleration equation. The forces you have are drag and weight. Drag has two components. One in the x-direction (Dx), one in the z-direction (Dz). Let's set the coordinate system at the point the jumper leaves the plane with the x-axis pointed out the nose of the aircraft and the z-axis pointed down. This means that the Dx is in the negative x-direction and Dz is in the negative z-direction. Consequently, weight (m*g) is in the positive z-direction. So your forces are F=-Dxi+(mg-Dz)k. Solving for a, you get a=F/m So your two equations of motion are d(dx/dt)/dt=-Dx/m d(dz/dt)/dt=(mg-Dz)/m To set this up for ode45 to solve in Matlab, you need these two equations and velocity equations. So let's use y to set up all of these equations. The output vectory will be [x, dx/dt, z, dz/dt]. So in the file called by ode45 set up ydot: ydot(1)=y(2); ydot(2)=-Dx/m; (where Dx is dependent on y(2), the x-velocity, as well) ydot(3)=y(4); ydot(4)=(mg-Dz)/m; (where Dz is dependent on y(4), the z-velocity) With this setup, the first line of the file would be function ydot=Johns9_25_equations(t,y) Then set up your variable, add the equations, and let it run. This should work pretty well. There maybe a couple typos that you can troubleshoot, but it gives you a place to start. You can make it much more complex by playing with the drag coefficient more, but that's a little overkill. Have fun! ************** For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return. ~Leonardo da Vinci~

You are getting close. You do have to set it up as second order. You absolutely must have the acceleration equations. That is how your forces are going to get factored in. As you have it now, you have forces in your velocity equations. Not where they are supposed to be. Also, your initial conditions are a mix of a velocity (85) and an acceleration (9.81), and it looks like these should both be velocities. The general framework of your m-files looks ok. I'll try to work through the equations real quick. I'm computer-less at the moment at home, so I'll see what I can come up with in the next few minutes before leaving work. ************** For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return. ~Leonardo da Vinci~

I think you need to add a little complexity to capture at least some of the dynamics of this problem. Since I really should get back to work, I'll just give you my initial impressions. First, set this up as a vector problem. It doesn't necessarily need to be 3-dimension. You can assume no lateral motion and limit motion to the xz-plane (horizontal and vertical motion). This will allow you to quantify the velocity as a vector as well. Initial horizontal velocity is 100 mph, initial vertical velocity is 0 mph. The direction of the drag vector is directly related to velocity. It's in the opposite direction. Second, start from the beginning to derive your equations of motion. Begin with the jumper's position in the xz space. You can set the (0,0) point as the exit point. Next take the derivative to get the velocity equation, and take the derivative again to get the acceleration equation. Depending on how you define everything, as in if you have a local coordinate system for your jumper, you may need to use the Transport Theorem to to make the derivatives work right. Use F=ma to get your equation of motion. Third, once you get these derived, there are several equations you need to input into Matlab. In the xz coordinate system, you would need the dx/dt, d(dx/dt)/dt, dz/dt, and d(dz/dt)/dt with all the forces and whatnot included. Put these in an m-file, set up a driver m-file, and use ode45 to solve the system of equations. It will output x, dx/dt, z, and dz/dt. This will tell you your final position in xz space, and you can do a quick calculation to determine where the plane is if it stayed at its original speed and direction. From there you can get the final distance they are from each other. Hope this helps. It seems like a fun problem. If I had more time (i.e., not at work), I'd derive it and give you some more concrete pointers. ************** For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return. ~Leonardo da Vinci~

+1

Core and upper body mainly. Though you could ask your trainer about functional training, which focuses more on compound movements more in line with how your body actually moves on a day to day basis. Aside from that, big compound movements would probably help the most. Maybe some isolation for a little spice, but definitely not as the focus of your workout program. ************** For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return. ~Leonardo da Vinci~

The uncomfortable part for me was the downwind leg of my landing pattern following a road alongside the airport that actually had a tiny bit of traffic that day. I was hoping there weren't any kids in those cars.... Anyway, I landed at the far end of the landing area, had a pair of shorts attached to my chest strap be rubber bands, and the pilot was terribly kind and tossed my shirt at me after he landed as I was walking in. I'd certainly do it again for a number and to support a fledgling organization.

Actually, I’m not a big fan of Yuengling but I am going to take the factory tour in Pottsville, PA next week just for the hell of it. Should be a nice ride and an interesting tour. Take the factory tour of St. Arnold's if you are ever in Houston. It's basically an excuse to get free/cheap fresh beer. You can bring lunch, too, and make an afternoon of it. ************** For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return. ~Leonardo da Vinci~

I can't imagine that's what the aircraft designers had in mind when they were doing the one engine out analysis.... ************** For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return. ~Leonardo da Vinci~

Ladydyver and I will both be there with our corsets. There should be lots of hookers around by the time were done! I may have to scrounge up some money and go to Chick's Rock. Jumping in a corset for social skydiving acceptance is a good way to meet new people, isn't it? ************** For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return. ~Leonardo da Vinci~

Yes, please. ************** For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return. ~Leonardo da Vinci~

That's what my coworker did. It worked well for all of us.