Question

The base of a solid is bounded by the curve y = sqrt (x+1) the x-axis and the line x = 1. the cross sections, taken perpendicular to the x-axis, are squares. find the volume of the solid.
a. 1
b. 2
c. 2.333
d. none of these
(will vote brainlest, like and rate)

Answer 1

See attached for a sketch of some of the cross sections.

Each cross section has area equal to the square of the side length, which in turn is the vertical distance between the curve y = √(x + 1) and the x-axis (i.e. the distance between them that is parallel to the y-axis). This distance will be √(x + 1).

If the thickness of each cross section is ∆x, then the volume of each cross section is

∆V = (√(x + 1))² ∆x = (x + 1) ∆x

As we let ∆x approach 0 and take infinitely many such cross sections, the total volume of the solid is given by the definite integral,

$\displaystyle \int_{-1}^1 (x+1) \, dx = \left(\frac{x^2}2 + x\right) \bigg|_{-1}^1 = \boxed{2} ~~~~ (B)$