i need someone to explain to me where i am making a mistake because i am getting an answer that differs from that of the book.(adsbygoogle = window.adsbygoogle || []).push({});

the solid lies between planes perpendicular to the x-axis at x = 0 and x = 4. the cross-sections perpendicular to the axis on the interval 0 ≤ x ≤ 4 are squares whose diagonals run from the parabola y = - sqrt x to the parabola y = sqrt x.

ok so...

the base of the square is a.

the diagonal is 2a^{2}.

the diagonal is 2 sqrt x.

so a^{2}, the area of the square, is sqrt x.

therefore,

{integral} from 0 to 4 of sqrt x

antidifferentiate and you get 2/3 x^{3/2}

plug in 4 and 0

final answer: 16/3

book says: 16

where did i mess up?

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Volume of the solid of revolution

**Physics Forums | Science Articles, Homework Help, Discussion**