volumes help (1 Viewer)

[VJ30]

find the volume when the circle x^2 + (y-4)^2=4 is revolved about the x-axis....can anyone show complete worked solutions...i am finding it tough to do!

 

[Beaconite]

sketch the circle, rotate in x-axis, use cylindrical shells method

 

[Beaconite]

Also, it is a circle so you have to find the two roots so you can calculate the radius

 

[VJ30]

sketch the circle, rotate in x-axis, use cylindrical shells method

Also, it is a circle so you have to find the two roots so you can calculate the radius

i dont get it wat do u mean the two roots?

 

[asianese]

http://community.boredofstudies.org/showthread.php?t=288591

I'm surprised you hadn't seen the exact same question here????

 

[VJ30]

http://community.boredofstudies.org/showthread.php?t=288591

I'm surprised you hadn't seen the exact same question here????

lol he is in my class! we are both idiots!

 

[asianese]

LOL!

What a coincidence. There are 2 solutions outlined (different methods - well 3) but yeah, that should be of help.

 

[VJ30]

LOL!

What a coincidence. There are 2 solutions outlined (different methods - well 3) but yeah, that should be of help.

in the shells method by nightweaver, he chose the bigger radius as y+delta y...but i chose y+delta y+2 since it is elevated by 2...am i wrong??? also for smaller radius he chose y where as i chose y+2...any difference?

 

[nightweaver066]

in the shells method by nightweaver, he chose the bigger radius as y+delta y...but i chose y+delta y+2 since it is elevated by 2...am i wrong??? also for smaller radius he chose y where as i chose y+2...any difference?

you should be taking the radius to be y + delta y and y as you are considering the distance of the y-coordinate to the x-axis.

if we were rotating around y = -2, then yes, you would consider y + 2 and y + 2 + delta y