Recent content by Jibobo

Wow, thanks. I must've been approaching the problem totally wrong. I kept trying to figure out how to use N!/(r!*(N-r)!) but I should've been thinking about 4 outputs (A, B, C, D), not just two (Success, Failure) to get: N!/[(N-b-c-d)! * (N-a-c-d)! * (N-a-b-d)! * (N-a-b-c)!] = 9!/[(9-2-2-1)! *...

My main inability is in figuring out how to represent those many different orders as some sort of easy to calculate formula because the brute force method of just rearranging and counting would take forever. I tried the brute force method to see if I could find something but nothing came to me...

Or what seems like it. I can't seem to figure how to apply the premutation or combination formulas to the following problem and it's driving me mad: "There are four types of objects: A, B, C, D. Enough are mixed together in a bag so that the probability of picking anyone of them out of the...

I've been having a lot of trouble with this problem. There's definitely something I'm missing and it most likely has to do with the force. "A mass m is thrown from the origin at t = 0 with initial three-momentum p_0 in the y direction. If it is subject to a constant force F_0 in the x...

Thanks a lot for the help. I am actually completely unfamiliar with rapidities and have done very little with hyperbolic trig functions, but I was still able to solve it through some terrible algebra after you told me that I was missing the y_BC term.

Since the y and z components are 0, I'm going to work with truncated 4-vectors. y_v = 1 / (1 - (v/c)^2)^0.5 y_u = 1 / (1 - (u/c)^2)^0.5 B_v = v/c B_u = u/c My work: From B to A V_B in B = V_BB = (c, 0) V_BA = (y_v...B_v*y_v * V_BB = (y_v*c, B_v*y_v*c) = (y_v*c, y_v*v)...

I'm a little rusty on this stuff, but basically, you're missing a term in the equation F = mg X sin (angle) - (static friction coeff.) X mg X cos (angle) that includes the given horizontal force. What you have right now is just F_total-parallel = F_gravity-parallel - F_friction. What you need...

Most textbooks derive this formula by taking the derivative of the Lorentz position transformation. However, I've been presented the problem of deriving it using four velocities and the Lorentz transformation matrix. Unfortunately I've been looking at it for hours and still don't know how to...

I actually have the same problem as well. But when I do out the problem, I don't get the same numbers you do and I don't see what I did wrong. I call one cleaver A and another B and set A as the origin in both inertial frames so that it's described by the 0 vector in both frames. Then B in...