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# simple harmonic motion Tweet

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1. simple harmonic motion
hey guys,
i cant understand how in SHM the acceleration is maximum in a pendulum/spring-mass system when then the velocity is negative.
i get it mathematically because at the point where V=0 the gradient is maximum negative/positive so therefore Acceleration is maximum negative or positive, but i dont understand it theoretically.
is the restoring force the unbalanced net force on the system?
resultant force =ma
is the net force on the system =
Driving force-restoring force=ma or = -kx ?
or is there no driving force? its just that i dont know what the force that is opposing the restoring force?
thanks
2. Re: simple harmonic motion
The greatest acceleration is not when velocity is negative, it's when it is zero.

Theoretically this should make sense since if acceleration is the rate of change of velocity, then the "greatest change" in this case is when the pendulum/mass changes direction - but to change direction it needs to stop moving in one direction before it can move in another - so there is a snapshot in time where v=0.

As for "Driving force-restoring force=ma or = -kx ?"; It's both. You equate them to get ma=-kx, which is the differential equation that defines SHM.
3. Re: simple harmonic motion
well, define V, and then find the differential of it. Take ln of both sides, and then square root both sides...

jk, i do media studies
4. Re: simple harmonic motion
The original driving force of the equation is determined by the initial conditions, which as this is a second order differential equation included the position and velocity.
5. Re: simple harmonic motion
(Original post by FireGarden)
The greatest acceleration is not when velocity is negative, it's when it is zero.

Theoretically this should make sense since if acceleration is the rate of change of velocity, then the "greatest change" in this case is when the pendulum/mass changes direction - but to change direction it needs to stop moving in one direction before it can move in another - so there is a snapshot in time where v=0.

As for "Driving force-restoring force=ma or = -kx ?"; It's both. You equate them to get ma=-kx, which is the differential equation that defines SHM.
thank you that makes sense