Recent content by pixel

You maybe don't understand what an "apparent contradiction" is. I said in my post that the contact point was at rest. There can be rolling with slipping on a surface with friction, given the right conditions.

Consider an object, say a ball, rolling at a constant speed without slipping to the right on a horizontal surface. Let's consider the ideal case, so no deformation of ball or surface. For rolling without slipping to occur, there has to be friction (static friction as the point on the ball that...

Let's say I am in an inertial frame of reference and I note two objects moving towards each other. Object 1 has velocity v1 to the right and object 2 has velocity v2 to the left. In my frame of reference, their speed of approach (relative speed according to me) is v1 + v2 which can be > c. But...

This raises doubts about some financial institutions using a caller's voice to verify identity. Maybe it's in conjunction with the caller's phone number.

Maybe it could have been worded better, but in the context of the article I think it is clear that the craft's velocity and the planet's velocity are w.r.t. the rest frame. With that understanding, the craft does leave the planet with original velocity + planet's velocity relative to the planet...

In the non-gravitational model I presented, the speeds are constant before and after the collision. In the case of a gravitational slingshot, the "initial" and "final" speeds are considered to be before and after the interaction (collision) so that they are again constant. It's just a...

Yes. I realized that as soon as I posted my question, hence the last paragraph that I added in edit.

A simple model often used to explain solar system gravitational slingshots is to consider a mass moving to the right with initial velocity v1i and a much larger mass moving to the left with initial velocity v2i. After the collision, the first mass is moving to the left with velocity v1f and the...

What I know of this only comes from popular presentations of the subject. So let's say there are two particles, A and B, known to have opposite values of a particular property such as spin. We don't know which particle has which spin until we measure the spin of one of the particles, say A. Then...

My understanding is that this tensor contains sources for spacetime curvature, analogous to how charge and current are sources for electric and magnetic fields. In other words, the elements of this tensor, such as mass density, are specified and used in the Einstein equation to solve for the...

I asked because he gave an example of a vector and a dual vector but I think I understand what you are saying is that the latter was not the dual of the former. To put things in concrete terms, can you give an example of a vector representing a physical quantity and its corresponding dual...

What is the metric in your example?

I've been looking at various online sources for relativity and have some confusion about "dual vectors." I'm hoping for some very basic information/examples from physics, not abstract mathematical concepts from the field of vector spaces. 1. In addition to the vector/dual vector distinction...

I appreciate the responses to my question and it will take me a bit of time to go through them before I can understand what was said. In the meantime, can you expand on your statement? What is the "that" that cannot be the same as the ship's frame?

Yes, that's what I was doing, hence my comment that I was hoping the details of how it got to the final velocity were not important.