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murielglass
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Angular acceleration of a merry-go-round - no time given!?
A merry-go-round accelerating uniformly from rest achieves its operating spped of 2.5rpm in 5rev. What is the magnitude of its angular acceleration?
2.5rpm=0.262rad/s
angular acceleration = change in angular speed / time
I've tried every possible thing I could think of. I actually know what the answer is (0.0011rad/s^2) but I can't find how they get to that. The teacher told me that if the final angular speed is 2.5rpm and it takes it 5rev to get that final angular speed, then t=2min.. but it doesn't make sense to me since the merrygoround is not moving at that final speed since t=0. plus, i don't get the right answer using t=120s. so I've tried calculating angular speeds for each revolution, assuming that in rev#1 the merry-go-round goes from 0 to 0.5rpm (=0.0524rad/s), from 0.5 to 1rpm, etc, averaging speeds and without averaging, but i keep getting it wrong. I'm guessing there's a conceptual issue I'm missing in this line of thought.
i figured out by the angular acceleration formula that t should equal 238.1s, but I want to know how they get to that number.
Homework Statement
A merry-go-round accelerating uniformly from rest achieves its operating spped of 2.5rpm in 5rev. What is the magnitude of its angular acceleration?
2.5rpm=0.262rad/s
Homework Equations
angular acceleration = change in angular speed / time
The Attempt at a Solution
I've tried every possible thing I could think of. I actually know what the answer is (0.0011rad/s^2) but I can't find how they get to that. The teacher told me that if the final angular speed is 2.5rpm and it takes it 5rev to get that final angular speed, then t=2min.. but it doesn't make sense to me since the merrygoround is not moving at that final speed since t=0. plus, i don't get the right answer using t=120s. so I've tried calculating angular speeds for each revolution, assuming that in rev#1 the merry-go-round goes from 0 to 0.5rpm (=0.0524rad/s), from 0.5 to 1rpm, etc, averaging speeds and without averaging, but i keep getting it wrong. I'm guessing there's a conceptual issue I'm missing in this line of thought.
i figured out by the angular acceleration formula that t should equal 238.1s, but I want to know how they get to that number.