# What is the surface area of a sphere with the radius 9?

You can find the surface area of a sphere by solving this equation: SA=4(pi)(r)(r) where SA is your surface area, and r is the radius.

Your answer comes out to be about 1017.4 square units.

### How many percent of the sun reach the earth surface?

That's a fairly easy calculation. The Sun is 93,000,000 miles away. The formula for the area of a sphere is 4/3*pi*r^2 The cross-sectional area of the Earth is a circle with a radius of about 4,000 miles. The formula for the area of a circle is pi*r^2. Google can be used as a calculator! The answer is (pi * (4000^2)) / ((4 / 3) * pi * (93 000 000^2)) = 1.38744364 × 10-9 So…

### What is the total surface area of a solid hemisphere of radius 9cm?

The surface area of a sphere is 4 x pi x r x r so in our case (since we have only half a sphere (hemisphere) the surface ares would be (0.5) x 4 x pi x 9 x 9 =162 x pi square cm. But now you have to add the area of the base because it gets exposed when youcuta sphere (to get the hemisphere) and the area of the base would be…

### An isolated conducting sphere whose radius R equals 1M has a charge 1.1nc the energy density at the surface of sphere?

The energy density at the surface of a charged conductor is the surface charge density squared , divided by 2 x the permittivity of free space. The surface charge density is the charge divided by the area it sits on. So if, e = permittivity = 8.85 x 10^-12 CC/Nmm and D = surface charge density, and U = energy density and R = radius of sphere and q = charge on sphere, then; U…

### As a cell grows larger how does its volume increase compared to it's surface area?

A1 If you simplify the image of a cell to that of a sphere, then you can use the equations for working out the volume or surface area as reference. The volume of a sphere = (4/3)*pi*(r^3), that is four thirds of pi multiplied by the radius of the sphere cubed. The surface area of a sphere = 4*pi*(r^2), that is four pi multiplied by the radius of the sphere squared. You can equate these…