How large is the "straightening torque"? (You can omit gravitational forces from your calculation; the gravitational torque is much less than this.)

A. \(2.3 \times 10^{-7} \mathrm{~N} \cdot \mathrm{m}\)

B. \(3.1 \times 10^{-7} \mathrm{~N} \cdot \mathrm{m}\)

C. \(2.3 \times 10^{-5} \mathrm{~N} \cdot \mathrm{m}\)

D. \(3.1 \times 10^{-5} \mathrm{~N} \cdot \mathrm{m}\)

The bunchberry flower has the fastest-moving parts ever seen in a plant. Initially, the stamens are held by the petals in a bent position, storing energy like a coiled spring. As the petals release, the tips of the stamens fly up and quickly release a burst of pollen. Figure P7.72 shows the details of the motion. The tips of the stamens act like a catapult, flipping through a \(60^{\circ}\) angle; the times on the earlier photos show that this happens in just \(0.30 \mathrm{~ms}\). We can model a stamen tip as a \(1.0-\mathrm{mm}\)-long, \(10 \mu \mathrm{g}\) rigid rod with a \(10 \mu \mathrm{g}\) anther sac at one end and a pivot point at the opposite end. Though an oversimplification, we will model the motion by assuming the angular acceleration is constant throughout the motion.

Transcribed Image Text:

Anther sac Pollen yright Initial configuration FIGURE P7.72 60 Pollen Stamen Final configuration 201