Calculus 1 : How to find volume of a region

Study concepts, example questions & explanations for Calculus 1

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Example Questions

Example Question #11 : Volume

Find the volume of the solid generated by rotating the shape bounded between the functions  and .

Possible Answers:

Correct answer:

Explanation:

The first step is to find the lower and upper bounds, the points where the two functions intersect:

Knowing these, the solid generated will have the following volume:

 

Example Question #12 : Volume

What is the volume of the solid formed when the function 

 

is revolved around the line  over the interval ?

Possible Answers:

Correct answer:

Explanation:

The disc method can be used to find the volume of this solid of revolution. To use the disc method, we must set up and evaluate an integral of the form

where and b are the endpoints of the interval, and R(x) is the distance between the function and the rotation axis. 

First find R(x):

Next set up and evaluate the integral:

Simplifying, we find that the volume of the solid is

Example Question #13 : Volume

Find the volume of the equation   revolved about the -axis. 

Possible Answers:

Correct answer:

Explanation:

This problem can be solved using the Disk Method and the equation 

.

Using our equation to formulate this equation we get the following.

 

Applying the power rule of integrals which states 

we get,

.

Example Question #14 : Volume

Find the volume of the area between  and 

Possible Answers:

Correct answer:

Explanation:

Graph1

Looking at the graph, we see that the curves intersect at the point  and  is on top.

Using the general equation 

 where  is on top.

This gives us that the volume is  

Example Question #15 : Volume

Find the volume of the region enclosed by  and  rotated about the line 

Possible Answers:

Correct answer:

Explanation:

The volume can be solved by 

 where  and  from 0 to 1 where the curves intersect.

Then, we formulate 

Example Question #16 : Volume

What is the volume of the solid formed by revolving the curve  about the  on ?

Possible Answers:

Correct answer:

Explanation:

We take the region and think about revolving rectangles of height  and width  about the line . This forms discs of volume . We then sum all of these discs on the interval and take the limit as the number of discs on the interval approaches infinity to arrive at the definite integral 

Example Question #11 : Volume

For any given geometric equation with one variable, volume over a given region is defined as the definite integral of the surface area over that specific region. 

Given the equation for surface area of any sphere, , determine the volume of the piece of the sphere from  to

Possible Answers:

Correct answer:

Explanation:

Recall that volume is the definite integral of surface area over a given region. 

Given our surface area formula, we can determine the volume in one step. 

 

Example Question #2901 : Functions

Find the volume of the solid generated by rotating the curve , for the range  around the x-axis.

Possible Answers:

Correct answer:

Explanation:

To solve this problem, treat the function

As the radius of a disc with infinitesimal thickness . This disc would then have a volume defined the surface area:

And a thickness or height:

The volume of the solid generated would be the sum of these discs, i.e. the integral:

Example Question #2902 : Functions

Find the volume generated by rotating the region between  and  around the -axis.

Possible Answers:

Correct answer:

Explanation:

Since the functions are being rotated around the y-axis, they should be rewritten. It may help to write them in terms of y:

And

Here, function designations  have been used solely to eliminate the ambiguity of using x for both functions.

Now, there are two points of intersection for these functions:

These will be the bounds for the integration to follow.

Finally, treat these two functions as the radii for two regions: a disk from the larger radius, and a hole from the smaller radius, allowing for the formation of a ring with a cross-sectional area:

These disks have infinitesimal thickness , and so the volume of the solid can be found by adding all of these disks together; i.e. by taking the integral:

 

 

Example Question #2903 : Functions

Find the volume of the function

 

revolved around the -axis on the interval .

Possible Answers:

 cubic units

 cubic units

 cubic units

 cubic units

Correct answer:

 cubic units

Explanation:

The formula for the volume of the region revolved around the x-axis on the interval  is given as

 

where .

As such,

 .

When taking the integral, we will use the inverse power rule which states,

 .

Applying this rule we get

 .

And by the corollary of the First Fundamental Theorem of Calculus

.

As such, the volume is

 cubic units.

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