Question

q17

Activities and Due Dates Chapter 9 Homework Resources Give Up? Feed Many caterpillars construct cocoons from silk, one of the strongest naturally occurring materials known. Each thread is typically 2.0 pm in diameter, and the silk has a Young's modulus of 4.0 x 10' N/m² N = 9.2 X10-15 strands Assuming that there is no appreciable space between the parallel strands, how many strands N would be needed to make a rope 8.2 m long that would stretch only 1.08 cm when supporting a pair of 85-kg mountain climbers? Incorrect Again assuming that there is no appreciable space between the parallel strands, what would be the diameter d of the rope? d = 0 cm Incorrect

Answer 1

Young's modulus of - -6 2 WL 코 WL AUL of YAL silk, Yz 4X10 N/m² diameter of each thread, d radius of each thread, a 21 mm = 10 m (l length, L= 8.2 m, extension, AL = 1.88 m = 1:08 x15 m Weight, W = 2x8x9.8=1666 N Young's modulus, Y= Aren cross-section, Az A = 3-16 x 10 4x109x108x U2 If N threads are used, then AzNTg2 ) Na 3.16 x 104 1.006x10 3-14X(106, 2 N=1.006x108 strands (17) Area of cross-section of the rope, A a d. 16 x 104 m² If d is the diameter of the rope, A= T d2 1666 x 8.2 2 m А. Tr2 8 Na 4 d? -4. 4A 4 x 3.16x10 - 4.025 x 10 3.14 - 2 d=2.006 X10 2.006 cm diameter, d= 2:00 6 x0² m