Calculus 1 : Calculus

Study concepts, example questions & explanations for Calculus 1

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Example Questions

Example Question #3931 : Calculus

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 #3931 : Calculus

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.

Example Question #3932 : Calculus

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,

 .

And by the corollary of the First Fundamental Theorem of Calculus

 .

As such, the volume is

 cubic units.

Example Question #21 : Regions

Find the volume generated by rotating the function  around the -axis over the interval .

Possible Answers:

Correct answer:

Explanation:

To approach this problem, treat the function  as the radius of a disc, with infintesimal thickness dx (which has the x-axis going through its center).

This infinitesismal volume of this disc is:

Now the volume of the solid rotated around the x-axis is the sum of these discs. In other word, it is the integral:

Note that the derivative of  is , so from this we can infer that the integral of  is :

Example Question #3931 : Calculus

Find the volume of the solid generated by rotating the parabola around the -axis, over the region where the function is greater than or equal to zero.

Possible Answers:

Correct answer:

Explanation:

In stating the bounds, the question is asking that we use those values of x where the function intercepts the x-axis:

Now, treat the function  as the radius of a disc with infinitesimal thickness . The volume of this disc is thus

And the volume can found via integration:

Example Question #3934 : Calculus

For this problem assume that volume  is given by:

, where  is the surface area function. 

Given the formula for surface area of a structure is given by 

Determine the volume function  of this structure. 

For this problem assume that  is not a function of  given below is a constant. 

Possible Answers:

Correct answer:

Explanation:

We're given that

Since the indefinite integral is with respect to , we can move the surface area function in front of the integral since we are told that  is not a function of 

Using the power rule, 

, where  is a constant. 

In our problem 

Therefore, volume can be given as

 

Example Question #2908 : Functions

Using the method of cylindrical disks, find the volume of the region of the graph of the function

on the interval .

Possible Answers:

 units cubed

 units cubed

 units cubed

 units cubed

Correct answer:

 units cubed

Explanation:

The formula for volume is given as

 

where .

As such,

 .

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

 .

Applying this rule term by term we get 

 

And by the corollary of the first Fundamental Theorem of Calculus,

As such, the volume is

 units cubed.

Example Question #2909 : Functions

Using the method of cylindrical disks, find the volume of the region of the graph of the function

on the interval .

Possible Answers:

 units cubed

 units cubed

 units cubed

 units cubed

Correct answer:

 units cubed

Explanation:

The formula for volume is given as

 

where .

As such,

 .

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

 .

Applying this rule term by term we get 

 .

And by the corollary of the first Fundamental Theorem of Calculus,

.

As such, the volume is

 units cubed.

Example Question #2910 : Functions

Set up the integral to find the volume of the solid if the region is bounded by  and , revolved about .

Possible Answers:

Correct answer:

Explanation:

For this problem, we will use the shell method.  Write the formula for the shell method.

The thickness of the shell is .

The radius of the shell is the distance from the y-axis to the vertical rectangles, .

The height of the shell is the top curve subtract the bottom curve.  The top curve is  and the bottom curve is .  The height is:  .

Determine the bounds by setting the top and bottom equations equal to each other.

Solve for  roots.

The roots are  and will be the bounds to the integral.  Write the integral.

Example Question #3935 : Calculus

Sphere segment

A sphere with a radius of 5 has a segment with perpendicular planes cut out of it, such as is pictured above.

If the first cut is 4 units to the left of the origin and the second cut is 2 units to the left of the origin, what is the volume of the segment?

Possible Answers:

Correct answer:

Explanation:

To approach this problem, begin by picturing how the sphere might be projected onto the two-dimensional Cartesian plane:

Sphere segment outlined

In its two-dimensional projection, we notice the outline of a circle. The formula for a circle of radius  in the Cartesian coordinate system is given as:

Which can be rewritten in terms of  as 

Now note the disk method of volume creation wherein we rotate a function around an axis (for instance, the x-axis):

The new function in the integral is akin to the formula of the volume of a cylinder:

 where  and 

The integral sums up these thin cylinders to give the volume of the shape.

Treating  as our , this integral can be written as:

Consider the points where circle contacts the x-axis, the greatest and smallest possible values of  on the circle:

This is how the volume of a sphere can be derived, and similary, this is how we can derive the area of our segment:

 

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