# All Questions

7 views

### A subsitute for Halliday

Our textbook in General Physics II is Halliday's book. As you may know in this book all multiple integrals are reduced to integrals by some tricks for taking elements. But I'd rather solve the ...
7 views

### Spring block problem

Basically in the question we have to find the minimum height from which we should drop the system ( masses 2m and m with a spring having spring constant k), such that the 2m mass just rises. The ...
6 views

### What would a universe that expands at a constant rate, that has no pressure, and no cosmological constant be like?

Consider a universe that is expanding at a constant rate, or that a double dot is zero, and there is negligible pressure and no cosmological constant. What are some of its properties?
13 views

### How do bubbles get their shape?

Since I have swam on the swim team for most of my life, I am very familiar with bubbles. I know a raindrop falling through the sky gets its shape because it is the most aerodynamic shape, but how come ...
9 views

### What would become of the earth's orbit if half of the sun's mass were suddenly to disappear?

I shall assume that the sun is at rest, so before the half mass disappear, the orbit of earth is an ellipse.
7 views

### Projectile Motion: Is this asking for maximum height or the final velocity of the y-component?

A dog in an agility show gets a running start, then leaps through a hoop, with an initial speed of 5 m/s, at an angle of 30 degrees, and attains a maximum height just as it goes through the hoop. ...
7 views

### Why to use the sign convention while solving problems as the mirror-formula itself is derived using the sign convention?

When we derive the mirror equation of concave mirror, i.e.,$\frac{1}{u}+\frac{1}{v}=\frac{1}{f},$ we've already used the sign conventions. Then why to use the sign conventions again while solving a ...
21 views

### How Can the Central Maximum in a Double Slit Experiment Have Greater Intensity Than the Original Beam

I have read in more than one place that the maximum intensity in a double slit experiment can be defined as the sum of the amplitudes of the light in each slit. For example, if the intensity of a ...
56 views

### How small would the patch of sun be that delivers heat to the earth?

The sun, being a ball, projects its EM radiation and light in all directions. We earthlings only receive a light from a portion of the sun, not all of it. What size is this patch of the sun's surface ...
24 views

### air craft physics

Just a fair warning, to many of you, this will no doubt be the most stupid question you've read today. I've been talking to Flat Earthers and they have brought up some physics questions that I ...
42 views

### Water bottle flipped upside down by itself. How is this possible? [on hold]

Someone told me they placed a water bottle right-side up on a marble counter like this: Turned like this all of a sudden with no further touching: Is this possible? If so, how can it happen?
16 views

21 views

### Does valid interpretations of quantum mechanics always reduce to trivial arguments about the equations?

I have put my question in the most compact form I could think of. It is quite long, so bare with me, for I have been thinking about this for years now. In the following, I will argue that the answer ...
12 views

### Numerically evaluating momentum sums

For many-body systems, calculations often involve momentum sums, which are ultimately evaluated numerically for a finite system size $N$. The larger $N$ is, the more accurate the results. Is there ...
10 views

### Calculating elastic collision at angle [on hold]

A block of mass m = 2.20 kg slides down a 30.0° incline which is 3.60 m high. At the bottom, it strikes a block of mass M = 6.60 kg which is at rest on a horizontal surface. (Assume a smooth ...
23 views

42 views

### Voltage and Energy in a capacitor [duplicate]

Well, my first question is related to the energy of the capacitor. Why does the energy of capacitor equals $E=\frac{1}{2}QV$ and not $E=QV$;in other words, why we multiplied it by $\frac{1}{2}$?? My ...
Suppose that the universe is dominated by matter and dark energy. Let $\Omega_m$ and $\Omega_\Lambda$ denote the respective relative density parameters. Given $\Omega_m$, what does $\Omega_\Lambda$ ...