Recent content by Amin2014

if light pulse is to the right, but moving car's velocity is to the left, we would expect c-v, but we get c instead which is greater. but if light pulse is to the right, and moving car's velocity is also to the right, we would expect c+v, but we get c instead which is smaller. how could the same...

Got it!

We need a basis to be able to express a vector in terms of coefficents. I don't know what your second question implies.

Given w = T (v), where T is a linear transformation and w and v are vectors, why is it that we can write any coefficient of w, such as w1 as a linear combination of the coefficients of v? i.e. w1 = av1 + bv2 + cv3 Supposably this is a consequence of the definition of linear transformations, but...

For the moment, there's an issue my my physicsforums page. The drop down menus don't function and I can't attach anything.

I've attached the problem and solution as picture. To my understanding, the gear E and the rod OB are taken together as the rotating rigid body. However, the equations of motion and (##∑F = macm##) are applied to the center of mass of the rod, G, rather than the center of mass of the rigid body...

I was validating your answer and completing it. The field would be zero only if the charge has dimensions.

Ok I see. The field is zero at the center of a spherical charge distribution, no matter the size of sphere. So if our charge had dimensions (unlike a point charge), then the field would be zero at the origin.

I checked some books and you are right. However, I don't understand why we can't we just assign it a value of zero? After all, the charge cannot apply force on itself.

Assuming the point charge lies at the origin, what is the electric field at the origin? Zero or undefined?

Thanks, I thought of this myself. Was wondering why no book suggested these. Good to know White has taken care of it.

The derivations of formulas in textbooks on thermodynamics and fluid mechanics seem to repeatedly make the assumption that the volume of whatever chosen control volume is constant, that's why I had to ask.

Control volumes are used to analyze transient and continuous processes alike; Refer to an engineering thermodynamics textbook. The point is that it's a mathematical tool that provides a different point of view from the lagrangian/control mass viewpoint. A transient process can lend itself to...

Did the volume change as well, or just the shape of the control surface?