The general equation to define SHM is

a=-w²x

if it's -w² then isn't the minus sign pointless seeing as it will be the same as +w²?
unless it's -(w²

Anyone know?

Also if it asks me in the exam what's the definition for SHM that I write? (not the equation)
Quote by Gaz_m2k5
The general equation to define SHM is

a=-w²x

if it's -w² then isn't the minus sign pointless seeing as it will be the same as +w²?
unless it's -(w²

Anyone know?

Also if it asks me in the exam what's the definition for SHM that I write? (not the equation)

The minus in phisics is generally for direction rather than a quantity because physics is the study of physical quantitys.

it took me a while to understand to but it is minus because of DIRECTION
I think in that it probably means -(w^2)
Unless it means -((W^2)x X )
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Uhm what?? No, like you said -w² = -(w² so the minus sign does make sence.
Quote by dazzler16
The minus in phisics is generally for direction rather than a quantity because physics is the study of physical quantitys.

it took me a while to understand to but it is minus because of DIRECTION

Yeah I understand the equation that the acceleration is always towards the centre so the opposite of the velocity, but if I get a question in the exam that says w=5 and x=2
is acceleration

-(5²2 = -50

or

-5²(2) = 50

EDIT: I guess seeing as the acceleration is towards the centre it would be -50 to oppose the velocity. But they should really write -(w²x in all these text books then.
Quote by Gaz_m2k5
Yeah I understand the equation that the acceleration is always towards the centre so the opposite of the velocity, but if I get a question in the exam that says w=5 and x=2
is acceleration

-(5²2 = -50

or

-5²(2) = 50

Is it going TOWARDS the centre cos then it will be + if it is going forward and - if it is reversing towards the centre

I would advise putting down the minus cos that is what I remember and I did it about 2 weeks ago.
Quote by Gaz_m2k5
The general equation to define SHM is

a=-w²x

if it's -w² then isn't the minus sign pointless seeing as it will be the same as +w²?
unless it's -(w²

Anyone know?

Also if it asks me in the exam what's the definition for SHM that I write? (not the equation)

As mentioned before, the minus sign is merely for direction. The minus sign is not a direction of w as w is only a scalar.

It might make more sense if you think of it as a = -X * w². The minus sign is referring to the direction of X i.e. position of the SHM object (whether it be a point on a wave or a block on a spring etc)

SHM equations are defined from the fact that the acceleration is directly proportional to the negative of the position (X).

I hope i didn't make things worse by not talking in simple language.
But the short answer is..yes..its like -(w²

EDIT:
Quote by Gaz_m2k5
Yeah I understand the equation that the acceleration is always towards the centre so the opposite of the velocity, but if I get a question in the exam that says w=5 and x=2
is acceleration

-(5²2 = -50

or

-5²(2) = 50

EDIT: I guess seeing as the acceleration is towards the centre it would be -50 to oppose the velocity. But they should really write -(w²x in all these text books then.

Just as a general rule -5²(2) and -(5²2 are the same thing..when you see -5² you should immediately assume that it is equal to -(5 * 5)
However it is different when it is (-5)²

So -5²(2) = -(5²2 = -50

But (-5)²2 = 50
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Last edited by NovaLau at Jan 19, 2007,
Quote by NovaLau
As mentioned before, the minus sign is merely for direction. The minus sign is not a direction of w as w is only a scalar.

It might make more sense if you think of it as a = -X * w². The minus sign is referring to the direction of X i.e. position of the SHM object (whether it be a point on a wave or a block on a spring etc)

SHM equations are defined from the fact that the acceleration is directly proportional to the negative of the position (X).

I hope i didn't make things worse by not talking in simple language.
But the short answer is..yes..its like -(w²

thanks.