تم الحل ✓
categoryإحصاء
schoolبكالوريوس
event_available2026-07-15
السؤال
Transcribed Image Text:
If two loads are applied to a cantilever beam as shown in the accompanying drawing, the bending moment at 0 due to the loads is a₁x₁ + a2x2
X2
↓
a₁
a2
0
(a) Suppose that X₁ and X2 are independent rv's with means 4 and 8 kips, respectively, and standard deviations 1.1 and 2.2 kip, respectively. If a₁ = 10 ft and a2 = 20 ft, what is the expected bending moment and what is the standard deviation of the bending moment? (Round your standard deviation to three decimal places.)
expected bending moment
kip-ft
kip-ft
standard deviation
200
45.354
(b) If X₁ and X2 are normally distributed, what is the probability that the bending moment will exceed 75 kip-ft? (Round your answer to four decimal places.)
0.9971
(c) Suppose the positions of the two loads are random variables. Denoting them by A₁ and A2, assume that these variables have means of 10 and 20 ft, respectively, that each has a standard deviation of 0.5, and that all A,'s and X,'s are independent of one another. What is the expected moment now?
kip-ft
200
(d) For the situation of part (c), what is the variance of the bending moment? (Round your answer to two decimal places.)
xkip-ft²
1.51
(e) If the situation is as described in part (a) except that Corr(X1, X2) = 0.5 (so that the two loads are not independent), what is the variance of the bending moment?
kip-ft²
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