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Old Oct 4th 2017, 05:34 AM   #1
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Does this question make sense or not?

"A passenger of mass 60kg is on a ferris wheel which moves in a vertical circle. The seat remains upright during the motion. The ferris wheel has a radius 13 m and the force exerted from the seat on the passenger at the bottom of the ferris wheel is 800 N. What is the constant velocity of the ferris wheel to 2d.p?"

Surely that when the person is at the bottom of the ferris wheel with no vertical acceleration then the force exerted must just be 60*9.8 not 800N? Also not to sure howto start working out the solution.

Any help would be apprictated.
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Old Oct 4th 2017, 06:04 AM   #2
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Yes, the question makes sense. The force exerted on the passenger when at the bottom of the wheel is equal to his weight PLUS the force required to accelerate him in the circle. If that centripetal force was not present the man would not be accelerating, and he would remain on the ground. From $\displaystyle \sum \vec F = m \vec a$, if we let F_s = the force applied to the man by the seat in the upward direction and mg is the force of gravity acting downward on the man, and we know the man is accelerating in a circular motion with a = v^2/R in the upward direction (towards the center of the Ferris wheel):

$\displaystyle \sum F = F_s - mg = ma$

$\displaystyle F_s = ma + mg = m \frac {v^2} R + mg$

Last edited by ChipB; Oct 4th 2017 at 07:11 AM.
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Old Oct 4th 2017, 08:52 AM   #3
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IF the person were sitting, motionless, at the bottom of the Ferris wheel (or, for that matter, at any point on the Ferris wheel) then the total force would be the weight. But if the person is in non-linear motion then there is an addition force causing that acceleration.
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