The bunchberry flower has the fastest-moving parts ever observed in a plant. Ini

Question

The bunchberry flower has the fastest-moving parts ever observed in a plant. Initially, the stamens are held by the petals in a bent position, storing elastic energy like a coiled spring. When the petals release, the tips of the stamen act like medieval catapults, flipping through a 60? angle in just 0.31 ms to launch pollen from anther sacs at their ends. The human eye just sees a burst of pollen; only high-speed photography reveals the details. As in the following figure shows, we can model the stamen tip as a 1.0-mm-long, 11 ?g rigid rod with a 11 ?g anther sac at the end. Although oversimplifying, we'll assume a constant angular acceleration.(Figure 1)

Part A

How large is the "straightening torque"?

Express your answer to two significant figures and include the appropriate units.

Explanation / Answer

length of rod = 1 mm = 0.001 meter

mass of rod = 11 ug = 11 x 10^-6 kg

mass of pod = 11 ug = 11 x 10^-6 kg

time = 0.31 milliseconds = 0.00031 seconds

Then...

angular displacement = 60 degrees = 1.0472 radians

angular acc = 2 * displacement / time^2 = 2*1.0472 / 0.00031^2 = 2.1794 x 10^7 N-m

moment of inertia = (1/3) m L^2 + mL^2 = (4/3) *11 x 10^-6 *0.001^2 = 1.463 x 10^-11

torque = inerta*angular acc = 1.463 x 10^-11 x 2.1794 x 10^7

torque = 0.0003188 N-m

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