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# m3 tips? watch

1. has anyone got any M3 tips? specifically with simple harmonic motion

when I'm asked to 'prove that this moves with SHM', I understand you always find an expression for acceleration = -k(displacement), but when it comes to vertical strings, horizontal springs, springs, etc... I find it hard to know what equation to form to reach this stage

does anyone have a rule or something in short which gives this?

EDIT:

to make my point clearer, with vertical springs you usually do T-mg=-a, so do you just use f=ma in all of them?
2. actually for mechanics ... A Slice of Pi
3. (Original post by Ummah dawn)
has anyone got any M3 tips? specifically with simple harmonic motion

when I'm asked to 'prove that this moves with SHM', I understand you always find an expression for acceleration = -k(displacement), but when it comes to vertical strings, horizontal springs, springs, etc... I find it hard to know what equation to form to reach this stage

does anyone have a rule or something in short which gives this?
You should always call your origin point the equilibrium point, so if it's on a string/spring, etc... always find the equilibirum then consider the extension from there. Call your extension then resolve forces in the direction of increasing so that you can use Newton's second law: , you should find all constant terms cancel out and you're left with an equation of the form as required.
4. okay thanks guys ill have a quick look at some more qs
5. (Original post by Ummah dawn)
has anyone got any M3 tips? specifically with simple harmonic motion

when I'm asked to 'prove that this moves with SHM', I understand you always find an expression for acceleration = -k(displacement), but when it comes to vertical strings, horizontal springs, springs, etc... I find it hard to know what equation to form to reach this stage

does anyone have a rule or something in short which gives this?

EDIT:

to make my point clearer, with vertical springs you usually do T-mg=-a, so do you just use f=ma in all of them?
To add to what Zacken said, you should be finding your tensions using Hooke's Law in terms of and you will notice that the terms that are not in terms of will cancel out quite nicely.
6. (Original post by TeeEm)
actually for mechanics ... A Slice of Pi
Looks like I'm a bit late but thanks for the recommendation
7. (Original post by A Slice of Pi)
Looks like I'm a bit late but thanks for the recommendation
my pleasure

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