12) A stroboscope is a light that flashes on and off at a constant rate. It can be used to illuminate a rotating object, and if the flashing rate is adjusted properly the object cant be made to appear stationary. What is the shortest time between flashes of light that will make a 3 blade propeller appear stationary when it is rotating with an angular speed of 16.7 rev/s? and what is the next shortest time?
20)A person is riding a bicycle and its wheels have an angular velocity of +20.0 rad/s. then the brakes are applied and the bike is brought to a uniform stop. during braking the angular displacement of each wheel is +15.92 revolutions. how much time does it take for the bike to come to rest and what is the angular accelerations in rad/s^2 of each wheel?
please show all work that you can even if you can only help with one of the problems. thanks so much!
2007-03-26 10:12:52 · 2 answers · asked by poker22only 2 in Science & Mathematics ➔ Physics
The minimum time between flashes will be the time it takes the propeller to rotate 1/3 revolution:
t = (1 rev/3) / (16.7 rev/s) ≈ 19.960 ms ≈ 20 ms. The next shortest time will be twice that, or 39.920 ms (40 ms)
ω^2 = 2αθ
α = ω^2 / (2θ)
α = 20.0^2 / (2(2π)(15.92)
α ≈ 1.9994 rad/s^2 ≈ 2 rad/s^2
2007-03-26 12:57:26 · answer #1 · answered by Helmut 7 · 0⤊ 0⤋
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2016-10-19 23:55:03 · answer #2 · answered by ? 4 · 0⤊ 0⤋