Recent content by Dark85

The wikipedia pages for the Particle horizon of the universe has the following statement: "Due to the expansion of the universe, it is not simply the age of the universe times the speed of light (approximately 13.8 billion light-years), but rather the speed of light times the conformal time."...

I see... well thinking about it, I guess the reason I asked that question was because I was kinda annoyed with the number of approximations made by the author in the lesson. Like not only this, he made a couple of other approximations so I just wanted to check if this especially was a legible...

Okay it may be so, but I felt using 3 prisms to approximate a lens is not so accurate...

The goal is to construct the ray diagrams for 3 parallel rays passing through a convex lens and to show that they converge at the focus.

So in my textbook, it is stated that "The refraction of light through a lens can be understood in a simple way by considering a lens as being made up of a set of prisms" But wouldn't this be an oversimplification? And for the ray diagrams(given below), this seems pretty far from a lens. To...

I was watching a video by Brian Cox on the Planck length. At 8 minutes and 31 seconds, he begins to talk about how one, in order to make an observation at size the Planck length, must use light of a tiny, tiny wavelength i.e. high energy photons(E=hf). He explains that so much energy goes into...

Thank you for pointing out my mistakes sir. I will redo it once more till i get a clear understanding. Once again, thank you.

Consider a body of mass m held above a rigid surface at a height h. Let the surface have such a large mass that any force exerted by the body during this entire scenario practically does not move the surface. This implies that before the body hits the surface and after hitting it, the momentum...

Hey i appreciate that but the reason I post my questions and doubts here is because i don't want to look it up. I want to hear it from experts like you and others on this platform. Rather, could you please suggest any book on the topic, I will go refer to it. Thank you.

What is rolling resistance exactly? Why is it more complicated than kinetic friction?

But it would be static friction since it rolls without slipping right?

I was also thinking even if one lifts the handlebars up, won't the decrease in the normal reaction force on the front wheel be compensated by an increase of the normal force on the back wheel. So it would just result in more friction on the back tire wouldn't it? It would just increase the wear...

Hey everyone, I have a question. Does pulling up on the handle bars make it easier to pedal. I believe it is true as by pulling up on the handle bars, the normal reaction force reduced which reduces friction(friction = coefficient of friction*normal force) which hence, makes it easier to pedal.

Right my bad, I thought you were referring solely to the case I mentioned above.

I did not understand how you got: ##x_1(t)=x_1(0)+v_1(0)t+\frac 1 2a_1t^2## i.e. why the term ##v_1(0)t## must be present. Won't ##\frac 1 2a_1t^2## be enough to calculate for displacement since it's an accelerated motion? The bodies start accelerating right from the time when they start moving.