Am self studying SHM, so sorry for the elementary questions.

Question

Would someone check/confirm some facts i think I've learned please.

1 If a sine wave graph starts at the origin at time = 0s, the sysyem is in equilibrium?

2 The amplitude at t= 0s is zero.

3 Same system, the phase angle/constant (phi) is 0 or pi?

4 When a system is displaced, but at rest, the phase angle is + or - half pi?

Confirmation or advice appreciated

Thanks

Answer 1

1. What does the sine wave represent?
2. Yes. If your sine wave is amplitude.
3. This makes no sense.
4. yes.

Answer 2

Sorry Bob,

The wave represents a simple pendulum.

In 3, I'm referring to the equation

x(t)=Asin(wt+(greek letter phi)), so was looking to confirm that in that specific circumstance I outlined, the value of phi would either be zero or pi (as in 22/7).

Thanks.