Check on a basic kinematic problem (FBD of a cabin on a Ferris wheel)

In summary, the weight force on the cabin is exerted by the structure, while the centripetal force (pointing towards the center of the wheel) is exerted by the passenger.
  • #1
greg_rack
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Homework Statement
Write and explain the free-body-diagram of the forces acting on a cabin of a Ferris wheel, in a uniform circular motion at the instant in which it's at the same height as the wheel's pivot point.
Relevant Equations
Standard motion equations
Hi guys,
Schermata 2021-01-29 alle 16.09.40.pnggiven the "blacker" to be the cabin under consideration,

I firstly wrote its weight force; then, my confusion started when drawing the force applied on the cabin by the structure(##F_{r}##).
I concluded it must have been both counter-acting the weight, and acting as a centripetal force... but I'm quite uncertain about it and I'd appreciate knowing if I'm correct or no.

The path I'm taking, for now, is that vertical component ##F_{ry}## must be equal to the weight, while the horizontal ##F_{rx}## to the centripetal force, resulting thus in an inclined force with respect to the standard vertical direction, pointing in the second quadrant of an ##xy## plane.

What do you think about it? Have I made any mistakes or imprecisions?
 
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  • #2
greg_rack said:
Homework Statement:: Write and explain the free-body-diagram of the forces acting on a cabin of a Ferris wheel, in a uniform circular motion at the instant in which it's at the same height as the wheel's pivot point.
Relevant Equations:: Standard motion equations

Hi guys,
View attachment 277031given the "blacker" to be the cabin under consideration,

I firstly wrote its weight force; then, my confusion started when drawing the force applied on the cabin by the structure(##F_{r}##).
I concluded it must have been both counter-acting the weight, and acting as a centripetal force... but I'm quite uncertain about it and I'd appreciate knowing if I'm correct or no.

The path I'm taking, for now, is that vertical component ##F_{ry}## must be equal to the weight, while the horizontal ##F_{rx}## to the centripetal force, resulting thus in an inclined force with respect to the standard vertical direction, pointing in the second quadrant of an ##xy## plane.

What do you think about it? Have I made any mistakes or imprecisions?
That's good. As far as your wording goes, I'd say ##F_{rx}## IS the centripetal force.

When you draw ##F_r## on your diagram, make sure you get its length/direction reasonably accurate. If drawn correctly, then 'by eye' (using the parallelogram method) you should see the vector-sum of ##F_r## and weight acts horizontally.

[EDIT: typo' corrected.]
 
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  • #3
And if you were asked to draw the FBD for a passenger in the cabin, you would draw an arrow parallel to the one you described above with a magnitude scaled by the ratio of the passenger's mass to the cabin's mass.

And if the passenger held a box of popcorn, ##\dots## you get the picture.
 
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1. What is a FBD (free body diagram) in a kinematic problem?

A FBD is a simplified diagram that shows all the external forces acting on an object. In a kinematic problem, it is used to analyze the motion of an object and determine the net force acting on it.

2. How do I draw a FBD for a cabin on a Ferris wheel?

To draw a FBD for a cabin on a Ferris wheel, you need to consider all the external forces acting on the cabin, such as gravity, normal force from the seat, and the tension in the cable. You can then use arrows to represent the direction and magnitude of each force.

3. What is the purpose of using a FBD in a kinematic problem?

The purpose of using a FBD in a kinematic problem is to simplify the analysis of the motion of an object by considering all the external forces acting on it. This allows us to apply Newton's laws of motion and solve for the acceleration, velocity, and position of the object.

4. How does the FBD change as the cabin moves on the Ferris wheel?

As the cabin moves on the Ferris wheel, the FBD will change depending on the position of the cabin. The direction and magnitude of the forces will change as the cabin moves up and down the wheel, but the same forces will still be present.

5. Can a FBD be used to solve for the motion of an object on a Ferris wheel?

Yes, a FBD can be used to solve for the motion of an object on a Ferris wheel. By analyzing the forces on the object, we can use Newton's laws of motion to determine the acceleration, velocity, and position of the object at any given time.

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