Surface area Definition and 440 Threads

Stephen hawking came to know of a study that stated that surface area of an event horizon increases. So he said that since area has increased Entropy also had increased. But why does surface area of an Event Horizon increase?

Hi How is circular surface area values square rooted ??. I am using this formula r2Xπ=mm2 to calculate the surface area of a circle but i want to know if there is a formula to get back to the diameter or the radius of the circle ?. example i have a circular surface area of 5.26mm2 and i want...

[FONT=Tahoma]I have been investigating the damping of an oscillating mass on a spring by a piece of card of varying surface area, in order to work out the damping constant λ for the equation y = A₀ e-λt sin(ωt). I took the natural log of the amplitude of each successive oscillation and plotting...

Is the air pressure acting on the top of the head of a person standing in a room equal to the air pressure acting on a same area on the floor of the same room? Since F = pA , it seems as if the air pressure is independent of the height of the surface on which it is acting. But that doesn't seem...

why surface area increases with foldings ,invaginations,roughness and powdered form?please someone explain concept of surface area. what is difference between perimeter or (circumference in case of circle)and surface area? Mentor Note: Two posts have been merged.

Homework Statement Find the area of that part of the cylinder x^2 + y^2 = 2ay that lies inside the sphere x^2 + y^2 + z^2 = 4a^2. Homework Equations [/B] If a surface S can be parametrized in terms of two variables u and v, then dS = Norm[dR(u,v)/du x dR(u,v)/dv]. The surface area is given...

Hey everyone, I was recently reading a paper on surface enhanced Raman scattering, and it mentioned that plasmons (and for that matter surface plasmon polaritons-where my interest lies) are sensitive to the surface to volume ratio of the structure. I can begin to understand intuitively with...

Homework Statement Homework Equations [/B] Surface area of sphere = 4*Pi*r^2, where r: is the radius of the sphere circleThe Attempt at a Solution Solution:[/B] 1. In terms of “r” and “R”, and the radius of sphere “S”, and “d”: Given that: · Surface area of both shaded area are equal...

I'm trying to follow Schwabl Thermodynamics, and I found the following equation for the surface area of a unit d-sphere: $$ \int d\Omega_d = \frac{2 \pi^{d/2}}{\Gamma(d/2)} $$ But this formula clearly fails for d=1: should be $$\pi$$ and d=2: should be $$ 4 \pi $$. What gives?

This is my first post but I have frequented the forum for a little while now. I tried to figure things out myself and often times I am lead here by google. So my question is this: How is the electric field of an object altered when the surface area of the object is altered? Example: Take a...

I am sure this should have already be discussed somewhere in the past... I have an intuitive problem with the area of a sphere. Following the mathematics of the metric and surfaces, I can easily derive the area of a sphere which is 4 \pi R^{2} . Now I'm have this problem: Suppose I get a ring...

I'm wondering how to scale up the surface area of a sphere of 6 million meters in radius, into a hypersphere of similar radius (i.e. a Hyper Earth). I would also like to know the ratio. I would like to know the basic value in 4th dimension, but knowing values for 5th, 6th, and higher would...

Homework Statement show rectangular box of given volume has minimum surface area when the box is a cube [gotta show it with partial derivatives to minimize] Homework Equations surface area = 2(wl+hl+hw) volume = whl The Attempt at a Solution so this is the one I would be minimizing...

For the first one, I'm completely dumbfounded. I used the SA formula for and ended up getting 2 $π\int_{π/6}^{0} \, cos2x * √1+4sin(2x)^2 ) $ And took u = sin2x, ultimately giving me $ π\int_{√3/2}^{0} \,d (1+ 4u^2)^(1/2) $ I'm lost as to what to do next. I'm almost definite that my...

find the area of the cylinder x^2+z^2=a^2 that is inside the cylinder x^2+y^2=a^2. my attempt: parameterise x^2+z^2=a^2 as a vector r(x,y) = (x,y,(a^2-x^2)^1/2). using the formula given here : http://tutorial.math.lamar.edu/Classes/CalcIII/SurfaceArea.aspx, I found the surface area = the...

if I am finding the surface area, and I am given the equation in term of x=g(y) about the x-axis, do i have to solve for y or can i just integrate in terms of y? would i just use dx/dy instead?

Hi, I have a question I'd like some help with which is related to my job working with drill rigs. Where you have a cylinder such as a drill string where the forces of the ground pressing in from all sides how much influence does the surface area have on the rotational force required to...

I'm wondering why my method for finding the surface area of a sphere is invalid. Essentially I'm integrating the perimeter of the circle perpendicular to the radius along the entire radius, and then multiplying by 2 (because the radius only covers half the sphere) (I hope that made sense...

i want to find V(t) At first i found this problem was very simple but when i try to write differential equations i ended up with these V' = kA that's for sure then i confined the problem only to spherical shape and no other shapes of raindrops involved as i can't express A in term of V alone(...

Is this so? I cannot think of a counter-example and it is too general a statement to prove.

Hi I'm doing a surface area problem with a parametric surface and I got the cross product but I can't figure out the double integral. I found the solution online but with no explanation, so can someone explain how to solve this integral: thank you!

Homework Statement Evaluate the definite integral for the surface area generated by revolving the curve about the y-axis: Homework Equations Curve: y=9-x^2 about y-axis The Attempt at a Solution Attached

Hi. I understand how to solve surface Area using integration when it is to be revolved about the x or y axis. But when the axis is not x or y I have a difficult time solving it. Please help me. Here is the equation sqrt(x+1) rotated at x=-1 and y=5. the bounds are 1 to 5. since y=sqrt(x+1)...

please tell me if i did this correctly: task: I'm trying to divide the differential dA by dV where.. dA = differential surface area of a sphere, dV = differential volume of a sphere dA=8\pirdr dV=4\pir2dr so then dA/dV= 2/r Also, if i treat this as a derivative, then would...

Hello, I'm new here, but I have some questions which i'd like to ask. I had this idea about corrugated wings to increase the wing surface area (thus increasing lift), but quickly realized that this would also increase the wings drag as it would have a larger cross section breaking through...

I would like to derive the surface area for an equation in the form of \(z = f(x, y)\). For example, if I have a sphere \((b^2 = x^2 + y^2)\), the surface area is circumference times arc length \((SA = 2\pi r\ell)\). Here I can take an arc and break it up into n parts to find the differential...

See image attached. (I've had a google but can't find anything). I am trying to understand the expression : Rdθ.2∏Rsinθ Here are my thoughts so far: Rdθ is the width of a strip, θ being the variable changing/to integrate over, giving arise to the elements. 2∏Rsinθ must then...

Using calculus, how would I derive a formula for the exposed surface area of a ball floating in water? For such a formula to be a good candidate, it would have to consider oscillations of the water and placid water. The surface area of a sphere is \(A = 4\pi r^2\).

Here's the problem I was given: Find the area of the surface generated by revolving the curve $$x=\frac{e^y + e^{-y} }{2}$$ from 0 $$\leq$$ y $$\leq$$ ln(2) about the y-axis. I tried the normal route first... g(y) = x = $$\frac{1}{2} (e^y + e^{-y})$$ g'(y) = dx/dy = $$\frac{1}{2} (e^y -...

Homework Statement Find the area of the surface generated by revolving the curve x=\frac{e^y + e^{-y} }{2} from 0 \leq y \leq ln(2) about the y-axis. The Attempt at a Solution I tried the normal route first... g(y) = x = \frac{1}{2} (e^y + e^{-y}) g'(y) = dx/dy = \frac{1}{2}...

The "s" in the geodesic equation refers to the "surface area" for that portion of the orbit around a star or black hole. For a small enough "delta t" the surface areas are the same. Around a small star the orbital surface area (without the other interfering gravitational sources) would...

Homework Statement A typical adult burns about 2500 Calories in one day. 1)How much energy does the average human emit every second 2)What is another term to use for expressing a “Joule per second”? 3)From your answers to (1) and (2), you just determined the “luminosity” of the average human...

consider the following image (the red is the surface area element and the green is the differential element that I'm integrating over) when we derived this in class, we treated the area formed by vectors a and b, as the area of a parallelogram. the thing is, a and b should be at right...

Homework Statement Obtain the surface area when the curve y=ex, 0≤x≤1, is rotated about the x-axis Homework Equations Surface Area = 2∏a∫b x√(1+(dy/dx)2)dx The Attempt at a Solution I started with the the equation, Surface Area = 2∏0∫1 x√(1+e2x)dx. However, whichever way I try to...

Homework Statement The shaded band shown here is cut from a sphere of radius Rby parallel planes hunits apart. Show that the surface area of the band is 2piRh. The image is on this site: http://imgur.com/TCx1weD http://imgur.com/TCx1weD The Attempt at a Solution How do I do...

Here is the question: I have posted a link there to this thread so the OP can view my work.

Here is the question: I have posted a link there to this thread so the OP can view my work.

Homework Statement f(x) = 1/x Interval [1, ∞) about the x-axis Set-up the integral for the surface area of the solid Then use the substitution u = x2 and integrate using the formula: ∫ sqrt(u2 + a2) / u2 du = ln(u + sqrt(u2 + a2) - sqrt(u2 + a2) / u + C a is a constant Homework...

I have to calculate the surface area limited with two functions: $$g(x)=2$$ and $$h(x)=\frac{4}{4x^2+1}$$ i was thinking first to calculate the points where this functions are intersecting by $$g(x)=h(x)$$ and to find corresponding $x$ for the intersection...and then to calculate definite...

Homework Statement Double Integral Surface Area of Spherical Ball radius Homework Equations ##\int_S d\vec{S} = 4*\pi*a^2## The Attempt at a Solution ##\int\int_0^a f(r,?) dr d? = 4*\pi*a^2##

I need to know the Surface Area and Volume of a spherical ball at the origin radius a. What I want is to evaluate the integrals at each integral. ##\oint_S dS =\int\int d? d? = 4 *\pi*r^2## ##\oint_V dV = \int_0^{\pi}\int_0^{2\pi}\int_0^a dr d\theta d\phi## = ##\frac{4}{3}*\pi*a^2##

The volume of a cube is increasing at a rate of $$\displaystyle\frac{10 cm^3}{\text {min}}$$ How fast is the surface area increasing when the length of an edge is $$\displaystyle 30 \text{ cm}$$ The answer to this is $$\displaystyle \frac{4}{3} \text{ cm}^2$$ $$V=x^3$$ and $$SA=6x^2$$ and...

Does anyone know what it is, or where I can find the surface area of a typical 60W incandescent bulb filament? (if possible, by GE) I'm working on a research project and we're applying the stefan-boltzmann law. I'm calculating an area around 3e-5 m^2. I figure I'm in the ballpark, but I'd...

Homework Statement I want the surface area of Revolution about x from [-2,2] of y = |x| So I want to know if I can take it x from [0,2] and just multiply this result by 2? Homework Equations The Attempt at a Solution Set up dy/dx = (5/(2√x)) S = 2 ∏ ∫ 5x^1/2(√ 1...

Homework Statement We have two animals. One of them is as big as an elephant or it's an elephant and the other one is a small animal as a cat. When we drop them from a high place, the smaller animal hurts less compared to the bigger one. Why? Homework Equations Surface area / volume The Attempt...

Homework Statement Which of the following integrals represents the area of the surface obtained by rotating the parametric curve x=t-t^2 y=(4/3)t^(3/2) 1<t<2 Homework Equations A = integral ( 2pi(y) * sqrt( 1+ (dy/dx)^2))dx The Attempt at a Solution I solved for dy/dx and got...

Homework Statement does surface area to affect the values of coefficient µk? Homework Equations frictional force =µk * normal force The Attempt at a Solution I know that if mass is larger then the frictional force is higher( f= ma) but how about the surface area? does it affect...

Is there any relationship between the surface area of a cube and the surface area of the cube's inscribed sphere? Jean~

Dear all, Does anyone know common symbols used to represent the ratio of two surface areas? The ratio is the surface area of low temp. heat exchanger divided by the total surface area of low and high temp. heat exchanger: AL/AT = area ratio, i want to find or create a symbol for. I would...

Homework Statement An industrial settling pond has a parabolic cross section described by the equation y = \frac{x^2}{80} . the pond is 40 m across and 5 m deep at the cetner. the curved bottom surface of the pond is to be covered with a layer of clay to limit seepage from the pond. determine...