Calculus AB : Calculus AB

Study concepts, example questions & explanations for Calculus AB

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Example Questions

Example Question #2 : Find Cross Sections: Squares & Rectangles

Let  be the region bounded by  and . Find the volume of the solid whose base is region  and whose cross-sections are rectangles perpendicular to the  axis with height .

Possible Answers:

Correct answer:

Explanation:

The cross-sections are perpendicular to the  axis; therefore, the volume expression will be in terms of

The area of a rectangle is . By applying this formula to our general volume formula , we get the following: .

Next, an expression for  must be determined. The problem specifies the length (or height) of the rectangle cross-sections is . This just leaves the value of  to be found. The width of the rectangle will vary as the region creating the base of the solid varies. The region is defined by the area enclosed between  and , therefore, .

Since the region is bounded by  and , the base has the following domain: .

Putting this all together, we find the following:

Example Question #712 : Calculus Ab

Let  be the region bounded by and . Find the volume of the solid whose base is region  and whose cross-sections are rectangles perpendicular to the  axis with height .

Possible Answers:

Correct answer:

Explanation:

The cross-sections are perpendicular to the  axis; therefore, the volume expression will be in terms of

The area of a rectangle is . By applying this formula to our general volume formula , we get the following: .

Next, an expression for  must be determined. The problem specifies the length (or height) of the rectangle cross-sections is . This just leaves the value of  to be found. The width of the rectangle will vary as the region creating the base of the solid varies. The region is defined by the area enclosed between and . The function  is rewritten in terms of  to become , because the final expression should reflect the fact that the cross sections should be written in terms of . Therefore, .

Since the region is bounded by  and , the base has the following domain: .

Putting this all together, we find the following:

 

Example Question #2 : Find Cross Sections: Squares & Rectangles

Identify the correct expression for the volume of a solid whose base is bounded by  and the  axis along , and whose cross-sections are rectangles perpendicular to the  axis with a height three times the width.

Possible Answers:

Correct answer:

Explanation:

The cross-sections are perpendicular to the  axis; therefore, the volume expression will be in terms of

The area of a rectangle is . By applying this formula to our general volume formula , we get the following: .

Next, an expression for  must be determined. The problem specifies the length (or height) of the rectangle cross-sections is three times the value of the width, or . The volume expression can now be modified: 

This just leaves the value of  to be found. The width of the rectangle will vary as the region creating the base of the solid varies. The region is defined by the area enclosed between  and , along . Therefore, .

Putting this all together, we find the following:

Example Question #3 : Find Cross Sections: Squares & Rectangles

Identify the correct expression for the volume of a solid whose base is bounded by  and  and whose cross-sections are squares perpendicular to the  axis.

Possible Answers:

Correct answer:

Explanation:

The cross-sections are perpendicular to the  axis; therefore, the volume expression will be in terms of

The area of a square is , where  is the side length of the square. By applying this formula to our general volume formula , we get the following: .

Next, an expression for  must be determined. Because s should be the width of the solid’s base, the expression for that length can be used to solve for

Since the region is bounded by  and , the base has the following domain: .

Putting this all together, we find the following:

Example Question #1 : Finding Volume Using Integration

Identify the correct expression for the volume of a solid whose base is bounded by  and  along  and whose cross-sections are squares perpendicular to the  axis.

Possible Answers:

Correct answer:

Explanation:

The cross-sections are perpendicular to the  axis; therefore, the volume expression will be in terms of

The area of a square is , where  is the side length of the square. By applying this formula to our general volume formula , we get the following: .

Next, an expression for  must be determined. Because  should be the width of the solid’s base, the expression for that length can be used to solve for

Putting this all together, we find the following:

Example Question #1 : Find Cross Sections: Squares & Rectangles

Find the volume of a pyramid whose base is a square with sides of length  and whose height is .

Possible Answers:

Correct answer:

Explanation:

First, it is important to consider the shape of this solid. This solid is a pyramid, with one square face and four triangular faces. Through a relationship of similar triangles, we are able to relate the known information (a height of  and a base side length of ) to our general variables for side length  and height of the pyramid . We can think of this plotted on the coordinate plane, with the width of the pyramid solid being in the  direction.

Since the side length  can be squared to find a general formula for the area of the pyramid’s base , this can be applied to the volume using cross-sections formula  as the next step. Note that the equation  solved for above is in terms of . Our new volume function, therefore, is also in terms of 

Because the pyramid reaches a maximum height of , and we assume the pyramid’s starting height is at , the appropriate bounds for the integral expression are: .

To wrap up this problem, combine the above information into one cohesive expression:

Example Question #1 : Find Cross Sections: Squares & Rectangles

Find the volume of the solid whose base is bounded by  and  and whose cross-sections are rectangles of height  and perpendicular to the  axis.

Possible Answers:

Correct answer:

Explanation:

The cross-sections are perpendicular to the  axis; therefore, the volume expression will be in terms of

The area of a rectangle is . By applying this formula to our general volume formula , we get the following: .

Next, an expression for  must be determined. The problem specifies the length (or height) of the rectangle cross-sections is . This just leaves the value of w to be found. The width of the rectangle will vary as the region creating the base of the solid varies. The region is defined by the area enclosed between and , therefore, .

Since the region is bounded by  and , the base has the following domain: .

Putting this all together, we find the following:

 

Example Question #3 : Finding Volume Using Integration

Identify the correct expression for the volume of a solid whose base is bounded by and and whose cross-sections are squares perpendicular to the  axis.

Possible Answers:

Correct answer:

Explanation:

The cross-sections are perpendicular to the  axis; therefore, the volume expression will be in terms of

The area of a square is , where s is the side length of the square. By applying this formula to our general volume formula , we get the following: .

Next, an expression for s2 must be determined. Because s should be the width of the solid’s base, the expression for that length can be used to solve for s2. 

Since the region is bounded by  and , the base has the following domain: .

Putting this all together, we find the following:

Example Question #1 : Find Cross Sections: Squares & Rectangles

Identify the correct expression for the volume of a solid whose base is bounded by a disk of radius  and whose cross-sections are squares parallel to the  axis.

Possible Answers:

Correct answer:

Explanation:

The cross-sections are parallel to the  axis; in other words, they are perpendicular to the  axis. This indicates that the expression should be in terms of .

Because the disk is of radius , the base is defined by the following formula:

The area of a square is , with s being the side length. By applying this formula to our general volume formula , we get the following: .

The radius  defines the bounds as being . Next,  can be found by understanding that  differs as the width of the circle changes. The value of  is the distance from one side of the circle to the other at any given point along . The length of one side of the square, therefore, is .

Putting it all together, the following is obtained:

Example Question #5 : Finding Volume Using Integration

Let  be the region bounded by , , and . Find the volume of the solid whose base is region  and whose cross-sections are squares perpendicular to the  axis.

Possible Answers:

Correct answer:

Explanation:

The cross-sections are perpendicular to the  axis; therefore, the volume expression will be in terms of

The area of a square is , where s is the side length of the square. By applying this formula to our general volume formula , we get the following: .

Next, an expression for  must be determined. Because s should be the width of the solid’s base, the expression for that length can be used to solve for

Since the region is bounded by and , the base has the following domain: .

Putting this all together, we find the following:

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