# SHM help

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#1
Just need some help on Simple Harmonic Motion,
My teacher says whenever you are given a graph with oscillations try to picture a pendulum, which I guess works for the moment.

The thing that confuses me are the equations given on the equation sheet,
For example if a question asks for maximum displacement and you have a graph of Displacement vs Time, the max displacment would be the peak right? So what's up with the equation x=ACos(wt) when would you have to input cos(wt) to find the displacement? same goes for the other ones e.g. v=-AwSin(wt).

Also where do these equations come from:
Vmax= 2*pi*f*x
Potential energy= 0.5*k*x^2
Kinetic Energy= 0.5*m*w^2*x^2
V=+/- w*(sqrt(k/m))*sqrt(x^2-A^2)
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2 years ago
#2
The use of sin/cos depends on where the oscillation is starting from, you could have an oscillation starting from its amplitude or equilibrium position, cos/sin respectively. (for displacement-time graph)
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