Recent content by cp255

I think I might have figure it out. a) The weak force is needed to produce nutrinos. b) If there are photons this implies EM c) Strong because of baryons. d) Weak because of neutrinos.

I have been getting ready for my Intro to Modern Physics final. The professor likes to ask a lot of questions like Which of the following neutron reactions proceeds via the electromagnetic force? Or something like this... I have been looking all over the internet and my textbook. All I can...

Homework Statement Consider a population model in which the birth and death rates and  of a cockroach population P are both proportional to sqrt(P). (Recall that in a “normal” exponential growth model, B and  D are constants.) If the cockroach population has increased from 100 to 400...

Homework Statement Positive charge Q is uniformly distributed around a semicircle of radius a. Find the magnitude of the electric field at the center of curvature P. Express your answer in terms of the given quantities and appropriate constants. Homework Equations The Attempt...

I will try it. The way I read the question is that each language generates a new one at the rate of 1.58 languages per 5860 years.

Yes but isn't L > 5860 at t = 1 because during the interval 0 < t < 1 other languages would have been generated since the growth is continuous.

I thought it made sense since each language is generating a new one at the rate of k languages per year. Therefore the total rate of change would just be the product of L and k.

Homework Statement There are now about 3300 different human "language families" in the whole world. Assume that all these are derived from a single original language, and that a language family develops into 1.58 language families every 5860 years. About how long ago was the single original...

I can see the screen shot of the question uploaded. I will rewrite the question and update the original post.

Homework Statement https://www.physicsforums.com/attachment.php?attachmentid=65556&stc=1&d=1389570667 For those who can not see the screen shot here is the question... Suppose the population P of rodents satisfies the diff eq dP/dt = kP^2. Initially there are P(0) = 2 rodents, and their number...

2. Water drains out of an inverted conical tank at a rate proportional to the depth y of water in the tank. Write a differential equation for y as a function of time. My answer was dy/dt = ky. This was from a weekly homework set where there were only 5 problems. I feel like I am missing...

Ok that makes sense. Now if the the magnitude of the cross product was not zero then B would have to equal C Right?

True or False, if AxB = AxC then either A=0 or B=C. A, B, and C are vectors and I thought this statement would be true. However the answer key says it is not. Why?

So what exactly is work then?

I was thinking that maybe although the energy went into the steam they system is the water which would have cooled.