Determining the Position as a Function of Time Equation

In summary, when setting up the Position as a Function of Time Equation for simple harmonic motion of a spring, one can use "sin" if the position starts at equilibrium (0) and "cos" if it starts at the maximum point. However, it may also depend on the phase angle phi and can be chosen based on aesthetics or other factors in the system being analyzed.
  • #1
jmason52
20
0
In simple harmonic motion of a spring, the Position as a Function of Time Equation is: x(t) = Acos(wt+phi). How does one determine whether to use "cos" or "sin" when setting up the basic equation from the data given in a problem? Is it as simple as: use "sin" when x starts at equilibrium position (0), otherwise use "cos"? Can one of you offer me a simple clarification? Thanks!
 
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  • #2
I believe it has to do with where it starts as you say. If it starts at the maximum point , you use cosine, if at 0 then sine.
 
  • #3
You might consider using whichever makes the phase angle phi a nice value (magnitude, sign). Basically it's a matter of aesthetics unless some other part of the system under analysis forces your hand.
 

1. What is the "Determining the Position as a Function of Time Equation"?

The "Determining the Position as a Function of Time Equation" is a mathematical formula used to calculate the position of an object at any given time, based on its initial position, velocity, and acceleration. It is often represented as x(t) = x0 + v0t + ½at2, where x(t) is the position at time t, x0 is the initial position, v0 is the initial velocity, and a is the acceleration.

2. How is the "Determining the Position as a Function of Time Equation" derived?

The equation is derived from the three basic equations of motion: x = x0 + vt (for constant velocity), v = v0 + at (for constant acceleration), and x = x0 + v0t + ½at2 (for constant acceleration). By combining these equations and solving for x, we get the "Determining the Position as a Function of Time Equation".

3. What are the units of measurement for the variables in the "Determining the Position as a Function of Time Equation"?

The units for x and x0 are usually meters (m), since they represent position. The units for v and v0 are often meters per second (m/s), since they represent velocity. The units for a are typically meters per second squared (m/s2), since it represents acceleration. The units for t are usually seconds (s), since it represents time.

4. Can the "Determining the Position as a Function of Time Equation" be used for objects with changing acceleration?

Yes, the equation can be used for objects with changing acceleration as long as the acceleration is constant at any given time interval. If the acceleration is changing continuously, the equation can still be used by dividing the motion into smaller intervals and calculating the position for each interval separately.

5. How accurate is the "Determining the Position as a Function of Time Equation" in real-world situations?

The equation is accurate as long as the object's acceleration remains constant and there are no external forces acting on the object. In real-world situations, this may not always be the case, so the equation may not be entirely accurate. Factors such as air resistance, friction, and other forces can affect the object's motion and may lead to slight discrepancies in the calculated position.

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