Question

4. Hanging by a Thread (2 pts). A spider spins a fine thread of spider silk between two posts a distance L0 apart. The thread has a diameter of d = 5 × 10-6 m and an equilibrium length of L0. When the spider (with mass m = 2 milligram) hangs from the center of the thread, the thread sags and stretches to support the weight of the spider, making an angle of θ = 10° below the horizontal, as shown.

a) Why must the thread sag when the spider hangs motionless from it?

b) Calculate the tensile strain ε in the thread and the Young’s modulus Y for the silk.

Answer 1