Simple harmonic motion (finding omega)

In summary, the velocity of a particle decreases as the displacement from the midpoint increases. At a displacement of 0.5cm, the velocity is half of its maximum.
  • #1
SteroidalPsyc
6
0

Homework Statement


A particle executes simple harmonic motion with an amplitude of 2.51cm. At what positive displacement from the midpoint of its motion does its speed equal one half of its max speed?


Homework Equations


A=2.51 cm
x(t) = Acos(wt)
v(t) = -Awsin(wt)
vmax = |-Aw|


The Attempt at a Solution


I just want to know how to find w so I can plug it into the vmax equation.
 
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  • #2
SteroidalPsyc said:

Homework Statement


A particle executes simple harmonic motion with an amplitude of 2.51cm. At what positive displacement from the midpoint of its motion does its speed equal one half of its max speed?

Homework Equations


A=2.51 cm
x(t) = Acos(wt)
v(t) = -Awsin(wt)
vmax = |-Aw|

The Attempt at a Solution


I just want to know how to find w so I can plug it into the vmax equation.

You actually don't need to plug it in. If [tex]v_{max} = Aw[/tex] then [tex]\frac{v_{max}}{2} = \frac{Aw}{2}[/tex]

Just use the energy equation

[tex]\frac{1}{2}kA^2 - \frac{1}{2}kx^2 = \frac{1}{2}mv^2[/tex]

where [tex]v= \frac{Aw}{2}[/tex], and remember to sub [tex]\frac{k}{m}[/tex] for [tex]w^2[/tex].
 
Last edited:
  • #3
novop said:
You actually don't need to plug it in. If [tex]v_{max} = Aw[/tex] then [tex]\frac{v_{max}}{2} = \frac{Aw}{2}[/tex]

Just use the energy equation

[tex]\frac{1}{2}kA^2 - \frac{1}{2}kx^2 = \frac{1}{2}mv^2[/tex]

where [tex]v= \frac{Aw}{2}[/tex], and remember to sub [tex]\frac{k}{m}[/tex] for [tex]w^2[/tex].

I don't know what k is though. How do I find k?
 
  • #4
Divide both sides by k!
 
  • #5
O ok haha sorry I'm really tired. Thanks for the help I solved it!
 
  • #6
You don't need the velocity or the angular frequency in order to answer the question. You're only asked at what displacement the velocity has half its maximum value.

[tex]x=A\cos{(\omega t)}[/tex]

[tex]v=-\omega A \sin{(\omega t)}[/tex]

[tex]v=-\omega A \sqrt{(1-\cos ^2 {(\omega t))}}[/tex]

[tex]v = -\omega \sqrt{(A^2-x^2)}[/tex]

[tex]|v|=\tfrac{1}{2} v_{max}=\tfrac{1}{2}\omega A[/tex]

[tex]\tfrac{1}{2}\omega A = \omega \sqrt{(A^2-x^2)}[/tex]

You don't always need all the constants involved in a problem in order to solve for a particular value. :)
 

Related to Simple harmonic motion (finding omega)

1. What is simple harmonic motion?

Simple harmonic motion is a type of periodic motion in which an object oscillates back and forth around an equilibrium position, with a restoring force that is directly proportional to the displacement from the equilibrium position. This type of motion can be found in many natural phenomena, such as a swinging pendulum or a vibrating mass on a spring.

2. How do you calculate the angular frequency (omega) in simple harmonic motion?

The angular frequency, denoted by the Greek letter omega (ω), is equal to the square root of the spring constant divided by the mass of the object. It can also be calculated by dividing the total number of oscillations by the total time taken for those oscillations.

3. What is the relationship between angular frequency and period in simple harmonic motion?

The period, represented by the letter T, is the time it takes for one complete cycle of the oscillation. The angular frequency is inversely proportional to the period, meaning that as the angular frequency increases, the period decreases and vice versa. This relationship can be expressed mathematically as T = 2π/ω.

4. Can the angular frequency change in simple harmonic motion?

Yes, the angular frequency can change depending on the parameters of the system. For example, if the mass or spring constant changes, the angular frequency will also change. It can also be affected by external forces such as friction or air resistance.

5. How is simple harmonic motion used in real-world applications?

Simple harmonic motion is used in many real-world applications, such as in the design of springs for cars and mattresses, the movement of pendulum clocks, and the behavior of molecules in a gas. It is also used in studying the properties of waves and analyzing sound and light waves.

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