Does it matter where between the axle and rim of the wheel you aim?
The wheel in Figure has eight equally spaced spokes and a radius of
. It is mounted on a fixed axle and is spinning at
You want to shoot a
long arrow parallel to this axle and through the wheel without hitting any of the spokes. Assume that the arrow and the spokes are very thin. What minimum speed(in m/sec) must the arrow have?
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The answer is 4.
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1 solution
time of revolution=1/2.5 s. time for 1 spoke to come to previous spoke position=1/2.5/8=1/20 s in 1/20th of second, arrow must completely pass through, so, speed=0.2 m/(1/20 s) =4 m/s