Thread: Amusement park problem.

Originally Posted by explodingtoenails

Mhm, I know that equation.

If the y-axis is h and the x-axis is t, would the equation be:

h(t) = 19cos24t - 19

I did the - 19 because the graph starts in the negatives.

attached is the graph of your position function ... period is not 15 seconds and the position is always negative. ???

I recommend you take some time to review the basics of trig graphs ...

Graphing Trigonometric Functions

Why isn't the period 15 seconds?

Originally Posted by explodingtoenails

Why isn't the period 15 seconds?

the period of motion is 15 seconds ... the graph of your function does not reflect that fact.

That's the problem I had from the beginning...I didn't know how to relate the motion to the height in an equation. I need help.

graph this equation and compare it to the first graph I posted ...



... then see if you can determine why it models the motion of a seat on the wheel.

I'll give my best go at it...

Uh 19 is half of 38, so it would go up 19 and down 19. Would it matter if it was -19 or positive 19?

Also, why is it cosine instead of sine? Would it matter since they are just the same graph with different translations?

2pi is one revolution, times t number of seconds, and it's divided by 15 because a revolution happens every 15 seconds.

19sin((2pi/15)t - pi/2) produces the same graph as the one you gave to me. I think I'm finally getting this!

a) 19sin((2pi/15)t - (pi/2))

b) 18.6 feet

c) I used the equation 27 = 19sin((2pi/15)t - (pi/2)) + 3 but apparently you can't arcsine anything greater than 1 so I'm not sure how to do this one.

Originally Posted by explodingtoenails

I'll give my best go at it...

Uh 19 is half of 38, so it would go up 19 and down 19. Would it matter if it was -19 or positive 19?

in this case, -19, because the graph of motion in a cosine curve reflected over the t-axis

Also, why is it cosine instead of sine? Would it matter since they are just the same graph with different translations?

easier to use cosine in this case ... no horizontal shift is necessary

2pi is one revolution, times t number of seconds, and it's divided by 15 because a revolution happens every 15 seconds.

that's right

hope you learned something

Can you help me out with part c, please? I don't know what I'm doing wrong.

as mentioned in the problem statement, the t-axis represents the middle of the wheel.

where would the ground be relative to the t-axis?

where would 27 ft above the ground be?

The ground would be 3 feet below the 19 foot radius of the wheel.

There's no way to specify where 27 feet above the ground would be.

Originally Posted by explodingtoenails

The ground would be 3 feet below the 19 foot radius of the wheel.

There's no way to specify where 27 feet above the ground would be.

if the bottom of the curve represents 3 ft above the ground, where would 27 ft above the ground be? come on ... THINK!

Uhhh it would be somewhere in the upper part of the curve. The maximum height is 41, so 27 is somewhere above the t-axis.

Originally Posted by explodingtoenails

Uhhh it would be somewhere in the upper part of the curve. The maximum height is 38, so 27 is somewhere above the t-axis.

now ... where exactly?