Surface Area of a Sphere Finding the surface

Finding the surface area of a sphere may not be as simple as finding

Surface area is the sum of the areas of all the faces or surfaces

The shape of the faces of these spatial figures are very familiar. Finding the

How about finding the surface area of sphere? How would its surface area be

Let this ball represents a sphere. Think of a way to determine the diameter

One way to determine the diameter of the ball is by placing it between

Now that the diameter of the ball is determined, get the ball of string.

Remember the diameter of the ball? Let us find out the number of circles

Form the string into circles having the same diameter as the ball. How many

Four circles with the same diameter can be formed from the string. What does

What do you notice about the area (A) of a circle and the surface

What is the formula for finding the surface area of a sphere?

Recall the diameter (d) of your ball? Using this diameter find the surface area

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Surface Area of a Sphere

Finding the surface area of a sphere may not be as simple as finding the surface area of other spatial figures like prism, cylinder, and pyramid.

Surface area is the sum of the areas of all the faces or surfaces of a solid figure. It is measured in square units. In determining the surface area (SA) of these solid figures, concepts learned in the past lessons may be applied. That is, getting the area of each of its faces and adding them together.

The shape of the faces of these spatial figures are very familiar. Finding the area of each shape have all been learned in the past lessons.

How about finding the surface area of sphere? How would its surface area be related to finding the area of the different shapes taught in the past lessons? Let us find out.

Let this ball represents a sphere. Think of a way to determine the diameter of the ball.

One way to determine the diameter of the ball is by placing it between two flat surfaces. The distance between these two flat surfaces represents the diameter (d) of the ball. Measure the diameter of the ball using a ruler. What is the diameter of the ball?

Now that the diameter of the ball is determined, get the ball of string. Wind the string around the ball. Then cut the string. You may use glue to facilitate winding of the string.

Unwind the string around the ball.

Remember the diameter of the ball? Let us find out the number of circles that can be formed from the string used around the sphere.

Form the string into circles having the same diameter as the ball. How many circles do you think can be formed from the string?

Four circles with the same diameter can be formed from the string. What does this mean?

What do you notice about the area (A) of a circle and the surface area (SA) of a sphere with the same radius r? It means that the surface area of a sphere with radius r is four times the area of a circle with the same radius r.

What is the formula for finding the surface area of a sphere?

Recall the diameter (d) of your ball? Using this diameter find the surface area of the ball. Remember that d = 2 r.