Related Rates: Particle Moving Along y=x^1/3, x=8, Theta Approx. 0.24 Rad

  • Thread starter Thread starter NIZBIT
  • Start date Start date
  • Tags Tags
    Related rates
Click For Summary

Homework Help Overview

The discussion revolves around a related rates problem involving a particle moving along the curve defined by y=x^1/3. The specific question is about determining the rate of change of the angle of inclination, theta, when x=8, given that x is increasing at a rate of 3 cm/s.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the need to define theta as a function of x rather than taking the derivative of a constant value. There are suggestions to visualize the problem by drawing a graph and identifying the right triangle formed by the curve and the axes.

Discussion Status

The conversation is active, with participants providing guidance on how to approach the problem. There is an emphasis on deriving expressions and understanding the geometric relationships involved, but no consensus has been reached on the final solution.

Contextual Notes

Participants are working within the constraints of a homework assignment, which may limit the information they can use or the methods they can apply. There is also a hint provided regarding the approximate value of theta when x=8.

NIZBIT
Messages
69
Reaction score
0
Code:
A particle is moving along the graph of y=x^1/3.  
Suppose x is increasing at the rate of 3 cm/s.  
At what rate is the angle of inclination, theta, changing when x=8?  
[Hint: when x=8, theta approx. 0.24 rad]
I'm stuck on problem. I know x=8, y=2 and the hyp=2.87. They want the derivative of theta so am I supposed to take the derivative of theta=0.24?
 
Physics news on Phys.org
No, you want to find some function that defines theta, and take the derivative of that.
 
NIZBIT said:
Code:
A particle is moving along the graph of y=x^1/3.  
Suppose x is increasing at the rate of 3 cm/s.  
At what rate is the angle of inclination, theta, changing when x=8?  
[Hint: when x=8, theta approx. 0.24 rad]
I'm stuck on problem. I know x=8, y=2 and the hyp=2.87. They want the derivative of theta so am I supposed to take the derivative of theta=0.24?
Well, the derivative of a constant (0.24) is 0 so that wouldn't do a whole lot of good would it? :wink: It's a lot more helpful to find the derivative of a function rather than a number! Draw a picture, showing the "angle of inclination" and write theta as a function of x. Then find the derivative of that function with respect to x. (Do you remember that the derivative of a function is the tangent of the angle the tangent line to the graph makes with the x-axis?)
 
yo.gif

Is this correct? Or am I completely off my rocker?:frown:
 
You're off your rocker. :biggrin:

Try following these steps:

1.) Draw a graph of f(x)=x1/3 vs. x.

2.) Consider an arbitrary point on the curve: (x,y)=(x,x1/3)

3.) Draw a line segment from the origin to (x,y) and drop a vertical line segment down from (x,y) to the x-axis. You now have a right triangle.

4.) The angle made by the line segment (the one connecting (0,0) to (x,y)) and the x-axis is the angle of inclination. Write down an expression for it in terms of x.

Try that and let's see what you come up with.
 
yup.gif

Is this right?
 
So far so good, but you're supposed to plug in x=8 and get a number for [itex]d\theta/dt[/itex].
 
Sweet! Thanks to all for the help!
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 4 ·
Replies
4
Views
5K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 10 ·
Replies
10
Views
6K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 2 ·
Replies
2
Views
14K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 10 ·
Replies
10
Views
3K
Replies
6
Views
3K