Simple harmonic motion and oscillation period

In summary, the object in SHM with a period of 4.0 s and amplitude of 10 cm moves from x = 0.0 cm to x = 6.0 cm in 0.41 seconds. Using the trigonometric identity, the equation can be simplified to x(t) = 0.10sin(1/2)πt. Solving this equation without using the identity will result in two possible answers, 1.59 s and 0.41 s, but the correct answer is 0.41 s. This is because cos^-1(0.06/0.01) is equal to 0.927, which is used in the second equation.
  • #1
05holtel
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Homework Statement



An object in SHM oscillates with a period of 4.0 s and an amplitude of 10 cm. How long does the object to move from x = 0.0 cm to x = 6.0 cm?

Homework Equations



x(t) = Acos(ωt +φ )

The Attempt at a Solution



ω = π/2
Acosφ = 0 ⇒φ = ±π/2
Since object is moving to the right choose φ = -π/2

x(t) = Acos(ωt-π/2)
=Asinωt
=0.10sin(1/2)πt

My question is how why does Acos(ωt-π/2) = =Asinωt
 
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  • #2
Acos(ωt-π/2) = =Asinωt

This is a standard trigonometric identity. The graph of the cosine function is a sine graph shifted by [itex]\pi/2[/itex]. Thus, if you add or subtract [itex]\pi/2[/itex] from the argument of a sine function, you'll get the cosine function and vice versa.
 
  • #3
OK, what if i solve this equation without using the trig idenitity

Apparently, there are then two possible answers,

either 0.927 = (pi/2)t - pi/2, which gives 1.59 s
or - 0.927 = (pi/2)t - pi/2. which gives 0.41 s

I know the answer is 0.41 seconds but why. Shouldnt I use the first equation because cos-1(0.06/0.01) is equal to postive 0.927
 

FAQ: Simple harmonic motion and oscillation period

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. This motion is characterized by a restoring force that is directly proportional to the displacement from the equilibrium position.

2. What is the formula for simple harmonic motion?

The formula for simple harmonic motion is x(t) = A cos(ωt + φ), where A is the amplitude, ω is the angular frequency, t is time, and φ is the phase angle.

3. How is the period of oscillation calculated?

The period of oscillation, represented by the symbol T, is the time it takes for one complete cycle of the oscillating motion. It can be calculated using the formula T = 2π/ω, where ω is the angular frequency.

4. What factors affect the period of simple harmonic motion?

The period of simple harmonic motion is affected by two main factors: the mass of the object and the stiffness of the restoring force. As the mass increases, the period also increases. Similarly, as the stiffness of the restoring force increases, the period decreases.

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

The frequency, represented by the symbol f, is the number of cycles per unit time. It is inversely proportional to the period, meaning that as the frequency increases, the period decreases. This relationship can be expressed as f = 1/T.

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