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A ferris wheel has a radius of 10 inches and is 2 inches off the ground. It makes a complete revolution every 10 seconds.

If a rider is directly horizontal to the center of the wheel and moving downward, find an equation that gives his height above the ground as a function of time .

1 Answer

5 votes

Answer:

y = -10·sin(πt/5) +12

Explanation:

You want the equation of the height of a rider of a Ferris wheel that has a radius of 10 and is 2 off the ground, with a period of 10 seconds, moving downward, starting from even with the center.

Equation

The general form of the equation will be ...

y = A·sin(2πt/T) + B

where A is a scale factor that is based on the radius and initial direction, and B is the height of the center of the wheel above the ground.

Height

We assume that 2 [units] off the ground means the low point of the travel is at that height. Then the middle of the wheel is those 2 [units] plus the radius of the wheel:

B = 2 + 10 = 12

Scale factor

The scale factor A will be the radius of the wheel, made negative because the initial direction is downward from the initial height. That is, ...

A = 10

Period

The period (T) is given as 10 seconds.

Height function

Putting these parameters together gives ...

y = -10·sin(2πt/10) +12

y = -10·sin(πt/5) +12

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Additional comment

We wonder if this wheel is really only 20 inches (20 in) in diameter, as that dimension seems suitable only for a model. We suspect it is probably 20 meters (20 m) in diameter.

Sometimes "m" is confused with "in" when it is written in Roman font and reproduced with poor resolution.

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A ferris wheel has a radius of 10 inches and is 2 inches off the ground. It makes-example-1
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