pendulum acceleration

[echoyjeff222]

I'm struggling to understand this question.... the setup is a basic pendulum. I understand how they do it, but what about TBR's way of saying the restoring force is F = - mg sintheta? Can't I just set that equal to ma and solve for acceleration, giving me a = gsintheta? Is this a different acceleration? I feel like I'm simplifying something.

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[pacer]

They are looking at acceleration in the x and y components.

Your method is partially correct but you only account for the x direction with ma = Fr = mgsintheta, so a (in x direction) = gsintheta