MHB Why Does dy/dt Equal Zero at the Endpoint of the Minor Axis?

  • Thread starter Thread starter zimsam
  • Start date Start date
  • Tags Tags
    Related rates
Click For Summary
SUMMARY

The discussion centers on the calculation of the derivative dy/dt at the endpoint of the minor axis for the equation (x-1)² + 2y² = 2. Participants confirm that dy/dt equals zero at the point (1,1), indicating a transition in the rate of change of y from increasing to decreasing. The implicit differentiation process is correctly applied, leading to the conclusion that while dy/dt is zero at this specific point, it does not imply that y is constant over time. The relationship dy/dx = (-dx/dt(x-1))/(2y) is also highlighted.

PREREQUISITES
  • Understanding of implicit differentiation
  • Familiarity with derivatives and their applications in physics
  • Knowledge of trigonometric functions, specifically arctangent
  • Basic concepts of planetary motion and its mathematical modeling
NEXT STEPS
  • Study implicit differentiation techniques in calculus
  • Explore the application of derivatives in physics, particularly in motion analysis
  • Learn about the geometric interpretation of derivatives in relation to conic sections
  • Investigate the behavior of functions at critical points and endpoints
USEFUL FOR

Students and educators in calculus, physicists analyzing motion, and mathematicians interested in conic sections and their properties.

zimsam
Messages
3
Reaction score
0
Screen Shot 2021-05-07 at 1.01.25 PM.png
 
Physics news on Phys.org
(a) $\dfrac{d}{dt}\bigg[(x-1)^2+ 2y^2=2 \bigg]$

you are given $\dfrac{dx}{dt}$ and the position of the planet.

use the derivative to calculate $\dfrac{dy}{dt}$

(b) hint …

$\theta = \arctan\left(\dfrac{y}{x}\right)$
 
skeeter said:
(a) $\dfrac{d}{dt}\bigg[(x-1)^2+ 2y^2=2 \bigg]$

you are given $\dfrac{dx}{dt}$ and the position of the planet.

use the derivative to calculate $\dfrac{dy}{dt}$

(b) hint …

$\theta = \arctan\left(\dfrac{y}{x}\right)$

When I find dy/dt, it comes out to =0 for me. dy/dx=(-dx/dt(x-1))/2y. Surely the rate of change of y is not zero...
 
zimsam said:
When I find dy/dt, it comes out to =0 for me. dy/dx=(-dx/dt(x-1))/2y. Surely the rate of change of y is not zero...

is that so … ?

AF0BC4B2-A1E4-4189-AA13-A9981948D0CA.png
 
skeeter said:
is that so … ?

View attachment 11130

I already know that dy/dt must be changing as well...
How did I make a mistake in my implicit differentiation?
 
zimsam said:
I already know that dy/dt must be changing as well...
How did I make a mistake in my implicit differentiation?

you didn’t make a mistake …

dy/dt = 0 at (1,1) which is at the endpoint of the minor axis

y is changing from increasing to decreasing w/respect to time at that position
 

Similar threads

  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 8 ·
Replies
8
Views
4K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 13 ·
Replies
13
Views
2K
  • · Replies 13 ·
Replies
13
Views
5K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 7 ·
Replies
7
Views
306