ch01-03 stress & strain & properties
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01 Solutions 46060 5/6/10 2:43 PM Page 30<br />
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1–43. Solve Prob. 1–42 assuming that pins D and E are<br />
subjected to single shear.<br />
3 ft 3 ft<br />
500 lb<br />
A<br />
Support Reactions: FBD(a)<br />
a +©M E = 0; 500(6) + 300(3) - D y (6) = 0<br />
D y = 650 lb<br />
B<br />
C<br />
3 ft<br />
; + ©F x = 0; 500 - E x = 0 E x = 500 lb<br />
1.5 ft<br />
1.5 ft<br />
3 ft<br />
+ c ©F y = 0; 650 - 300 - E y = 0 E y = 350 lb<br />
Average shear <strong>stress</strong>: Pins D and E are subjected to single shear as shown on FBD<br />
(b) and (c).<br />
D<br />
300 lb<br />
E<br />
For Pin D, V D = F D = D y = 650 lb<br />
(t D ) avg = V D<br />
A D<br />
=<br />
650<br />
p<br />
4 (0.252 )<br />
= 13242 psi = 13.2 ksi<br />
Ans.<br />
For Pin E, V E = F E = 2 500 2 + 350 2 = 610.32 lb<br />
(t E ) avg = V E<br />
= 610.32<br />
p<br />
A E 4 (0.252 )<br />
= 12433 psi = 12.4 ksi<br />
Ans.<br />
*1–44. A 175-lb woman stands on a vinyl floor wearing<br />
stiletto high-heel shoes. If the heel has the dimensions<br />
shown, determine the average normal <strong>stress</strong> she exerts on<br />
the floor and compare it with the average normal <strong>stress</strong><br />
developed when a man having the same weight is wearing<br />
flat-heeled shoes. Assume the load is applied slowly, so that<br />
dynamic effects can be ignored. Also, assume the entire<br />
weight is supported only by the heel of one shoe.<br />
Stiletto shoes:<br />
A = 1 2 (p)(0.3)2 + (0.6)(0.1) = 0.2014 in 2<br />
s = P A = 175 lb<br />
= 869 psi<br />
2<br />
0.2014 in<br />
1.2 in.<br />
0.5 in.<br />
Ans.<br />
0.3 in.<br />
0.1 in.<br />
Flat-heeled shoes:<br />
A = 1 2 (p)(1.2)2 + 2.4(0.5) = 3.462 in 2<br />
s = P A =<br />
175 lb<br />
= 50.5 psi<br />
2<br />
3.462 in<br />
Ans.<br />
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