Physics - 16.5 Simple Harmonic Motion - 2 Springs (4 of 5) 2 Springs in Series, 1 Mass

In this video I will find v(x)=?, a(x)=?, k(eq)=?, w0=? of a block attached to 1 spring in series to a 2nd spring (2 different spring constants) which is attached to a ceiling.

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[talashka]

Michel, should A^2-x^2 be equal to zero? because it seems that A^2 and x^2 are the same value. if so, then velocity would be equal zero. no?

[raymondmimay]

Why is gravitational force not factored into the equation F=ma?

Also the gravitational potential energy some time after we let go of the spring? I get that the gravitational potential energy is cancelled at the equilibrium point but it changes as the mass moves up and down.

[dhirajdeepa]

Can you explain the first statement of calculaiton of K(eq).