________________________________________________________________________
PROBLEM (*12.90) A rigid block weighing W = 2 kips is placed over the top of a 4-in. nominal
diameter steel pipe (see Table B.7), as shown in Fig. P12.90. What is the speed v of the block when it is
just over the top of the pipe, if after impact, the largest stress developed in the pipe is 30 ksi?
Given: E = 29 x 106 psi y
σ
= 36 ksi (from table B.4) A = 3.17 in.2 (from Table B.7).
Assumption: Steel will not fail by yielding or buckling
*SOLUTION
We have 32
2 10 386 5.181 .mWg lbsin==× = ⋅
Therefore
max max
max max
; 30 , 95.1
3.17
PP
Pk
A
σ
== =
ips
Use Eq. (12.62):
22
3
max (5.181) (3.17)(29 10 )
; 95.1 10 20
mv AE v
PL
×
=×= 6
Solving,
19.49 .vi=ns
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