40000=5000e^30r
40000/5000=e^30r
R=(log(40000/5000)/log(e))/30)*100
R=6.93%
I think it is 9 that it ok
Answer:
Step-by-step explanation:
Given:
elongation, x = 0.50 in
Force, f = 9000 lb
Young modulus, E = 10,000,000 psi
Maximum Stress, Sm = 30000 psi
Length, L = 16 ft
Converting ft to in,
12 in = 1 ft
=16 × 12 = 192 in
Young modulus, E = stress/strain
Stress = force/area, A
Strain = elongation, x/Length, L
E = f × L/A × E
1 × 10^7 = stress/(0.5/16)
= 26041.7 psi
Minimum stress = 26041.7 psi
Maximum stress = 30,000 psi
Stress = force/area
Area = 9000/26041.7
= 0.3456 in^2
Stress = force/area
Area = 9000/30000
= 0.3 in^2
Using minimum area of 0.3 in^2,
A = (pi/4)(d^2)
0.3 in^2 = (pi/4)(d^2)
d = 0.618 inches
diameter, d = 0.618 inches
Answer:
2.29 ft of side length and 1.14 height
Step-by-step explanation:
a) Volume V = x2h, where x is side of square base and h is hite.
Then surface area S = x2 + 4xh because box is open.
b) From V = x2h = 6 we have h = 6/x2.
Substitude in formula for surface area: S = x2 + 4x·6/x2, S = x2 + 24/x.
We get S as function of one variable x. To get minimum we have to find derivative S' = 2x - 24/x2 = 0, from here 2x3 - 24 = 0, x3 = 12, x = (12)1/3 ≅ 2.29 ft.
Then h = 6/(12)2/3 = (12)1/3/2 ≅ 1.14 ft.
To prove that we have minimum let get second derivative: S'' = 2 + 48/x3, S''(121/3) = 2 + 48/12 = 6 > 0.
And because by second derivative test we have minimum: Smin = (12)2/3 + 4(12)1/3(12)1/3/2 = 3(12)2/3 ≅ 15.72 ft2
The answer is <span>A. 2 eggs / 3 cups of flour = 12 eggs / 18 cups of flour because 2 x 18 = 3 x 12 = 36.</span>
