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## Homework Statement

[Let a Ferris wheel exist.] The wheel carries 36 cars, each holding as many as 60 passengers of 70kg mass, around a circle of radius R = 38m. The mass of each car is about 1.1e4 kg. The mass of the wheel's structure as about 6.0e5kg, which was mostly in the circular grid from which the cars are suspended. Find the rotational inertia around the center of the wheel.

## Homework Equations

I=MR²

L = Iω

## The Attempt at a Solution

Divide the inertia into two parts, inertia of the cars and inertia of the wheel:

I_cars = MR²

M = [36 ( 1.1e4 + 60 x 70)] kg

R² = 38² m²

I_wheel = MR²

M = 6.0e5 kg

R² = 38² m²

Total inertia is calculated to be 1.7e9

Answer: 1.22e9

According to the solution, M for the wheel should be 3.0e5 kg, but I don't understand why.

Thanks in advance! (also, please give suggestions for homework problem format, this is my first)