Recent content by Unsilenced

Ah, I found where the sign flip came in. Values are now 4 and 5, and the roots what they should be, assuming I had the correct roots to begin with.

Characteristic equation: a^2-4a+1=0 Using the quadratic formula gets me a=2+/-sqrt(3) x=C1e^(2+sqrt3)+C2e^(2-sqrt3) ... Did I do something wrong? Um, negative would appear to be correct. Sorry.

So, I dropped the 3 and the 4 and used Euler's formula to turn them into exponentials. I ended up with x=ie^((-2-i)t)-ie^((-2+i)t) Does that mean my roots are -2 +/- i? Or do I have to go further?Edit: Working through, I got k=5 r=-4 Seems like a legit answer, but was dropping the i...

Homework Statement x''(t)+r*x't+kx=0 Suppose that for some initial conditions the solution is given by x=e^(-2t)*(3cos(t)+4sin(t)) What are are and k? Homework Equations See aboveThe Attempt at a Solution I've tried to "brute force" the solution simply by sticking the expression for x...

Yeah, that does make it a bit easier to visualize. In the case of a bullet hitting a metal plate, the medium tends to be denser than the projectile, and all sorts of deformation occurs. In real life this equation would look a bit more like this: http://i.imgur.com/2KA5jiv.gif :p A...

Ah, I see. So it is meant to be asymptotic? I thought it might be, but it didn't make sense from a physical interpretation, I.E that the bullet never stops moving.

Acceleration becomes more negative, that is, deceleration increases with velocity. So, I could make both terms negative? Switching the signs in the initial equation only changes whether R is positive or negative. That doesn't solve the fact that my final equation is mathematically impossible.

Homework Statement A bullet of mass m strikes an amor plate with initial velocity v0. As the bullet burrows into the plate, its motion is impeded by a frictional force which is directly proportional to the bullet's velocity. There are no other forces acting on the bullet. -Use Newton's Second...