The strength of a rectangular beam varies directly as the square of it depth. If the strength
of a beam 10 inches deep is 3600 pounds per
square inch, what is the strength of a beam four
six inches deep?

For a beam with rectangular shape (width ‘b’, height ‘h’), the section modulus which decides the strength is expressed as:

W = b*h^2/6

At the same time:

b^2 + h^2 = 60^2

From the above equations:

W = b*(60^2 - b^2)/6 = (-b^3/6 + 3600*b/6)

The value of ‘W’ is maximum when dW/db = 0

dW/db = d/db( (-b^3/6 + 3600*b/6)) = -b^2/2 + 600 =0

From the above: b = sqrt(1200) = 34.64 cm,

and h = sqrt(3600 - b^2) = 49.00 cm

(Check sqrt (34.64^2 + 49^2) = 60.01 cm = D)

Step-by-step explanation:

Direct variation equation:

In this case it is:

Substitute the given values and solve for k:

The equation becomes:

Now, find the value of y, when x is 6:

Note, I took the depth as 6 inches but the question is a bit confusing by saying "four six inches". If it is 4 inches then your answer will be:

what are the statments

step-by-step explanation:

hello!

to begin with, we're given that on earth, a rock weighs 20 pounds, and while on jupiter, that same rock weighs 42 pounds. now, we're trying to find the weight of a rock that weighs 10.5 pounds on earth, on jupiter.

to solve this, first, set up a proportion, cross-multiply, and solve it algebraically.

setting up the proportion is the hardest and the most confusing part of the problem, but it's simple.

if on earth, the rock weighs 20 lbs, and on jupiter it weighs 42 lbs, our first part of our proportion is 20/42 lbs. the second part has to be equal to each other. this means that 10.5 has to be on the numerator of the fraction, and x, the value we're trying to find, has to be on the denominator. remember that the rock weighs 10.5 lbs on earth, and we're trying to find the weight of it on jupiter (which is x).

20/42 = 10.5/x

next, you would cross-multiply.

20x = 42(10.5)

20x = 441

now, solve it algebraically by using division.

x = 22.05 lbs

this can be rounded to 22.1 lbs.

therefore, the weight of the rock on jupiter is 22.1 lbs, the fourth choice.