Equation for underdamped harmonic motion

In summary, the equation of underdamped harmonic motion is x(t) = C cos(wt) + D sin(wt). When assuming the function x(t) is real, the real and imaginary parts of the equation, A and B respectively, are related as A = B. This means that when A and B are conjugates, A + B is a real number and A - B is a complex number.
  • #1
pinkcashmere
18
0
I found an explanation for the equation of under damped harmonic motion, x(t) = C cos(wt) + D sin(wt), but I was wondering if someone could further explain why:

- "However, if you assume the function x(t) is real, then they are related as A = B
- why is (A-B) is imaginary
 

Attachments

  • question.png
    question.png
    34.4 KB · Views: 324
Mathematics news on Phys.org
  • #2
If A and B are conjugates, A = (g,h) and B = (g,-h).

A + B = (g,h) + (g,-h) = (2g,0). This is a real number.
A - B = (g,h) - (g,-h) = (0,2h). This is a complex number.
 
  • #3
spamanon said:
If A and B are conjugates, A = (g,h) and B = (g,-h).

A + B = (g,h) + (g,-h) = (2g,0). This is a real number.
A - B = (g,h) - (g,-h) = (0,2h). This is a complex number.

thanks,
can you also explain the "However, if you assume the function x(t) is real, then they are related as A = B" bit
 

What is the equation for underdamped harmonic motion?

The equation for underdamped harmonic motion is x(t) = Ae-btcos(ωt+φ), where x(t) is the displacement, A is the amplitude, b is the damping coefficient, ω is the angular frequency, and φ is the initial phase angle.

What does underdamped harmonic motion mean?

Underdamped harmonic motion refers to a type of oscillatory motion where the damping force is not strong enough to bring the system to rest. This results in the object oscillating back and forth around its equilibrium position with gradually decreasing amplitude.

What is the significance of the damping coefficient in the equation for underdamped harmonic motion?

The damping coefficient, b, determines the rate at which the amplitude of the oscillations decreases. Higher values of b indicate stronger damping, which results in faster decay of amplitude and shorter duration of oscillations.

How does the initial phase angle affect underdamped harmonic motion?

The initial phase angle, φ, determines the starting position of the object at t=0. It does not affect the amplitude or frequency of the motion, but it does affect the position of the object at any given time in the motion.

What is the relationship between the angular frequency and the natural frequency in underdamped harmonic motion?

The natural frequency, ω0, is equal to the square root of the ratio of the spring constant, k, to the mass, m, in the system. The angular frequency, ω, in underdamped harmonic motion is equal to ω0 multiplied by the square root of 1-b202. This relationship shows that the damping coefficient affects the angular frequency and thus the period of the oscillations.

Similar threads

Replies
4
Views
416
  • Introductory Physics Homework Help
2
Replies
51
Views
2K
Replies
1
Views
416
  • Introductory Physics Homework Help
Replies
16
Views
408
Replies
4
Views
1K
  • Classical Physics
Replies
11
Views
1K
  • Classical Physics
Replies
4
Views
802
  • Introductory Physics Homework Help
Replies
5
Views
840
Replies
7
Views
646
Replies
35
Views
3K
Back
Top