# M3: SHMWatch

#1
what would be the amplitude? we've stretched it so that the RHS is smaller than it's natural length.
0
3 months ago
#2
(Original post by Maths&physics)
what would be the amplitude? we've stretched it so that the RHS is smaller than it's natural length.
IIt's a spring not a string. The natural length of a single spring would be the center of the resulting SHM.
0
3 months ago
#3
The question says springs not strings.
0
#4
(Original post by mqb2766)
IIt's a spring not a string. The natural length of a single spring would be the center of the resulting SHM.
brilliant! how did you know I misread the word spring for string?!

"The natural length of a single spring would be the center of the resulting SHM." what do you mean?
0
#5
(Original post by old_engineer)
The question says springs not strings.
(Original post by mqb2766)
IIt's a spring not a string. The natural length of a single spring would be the center of the resulting SHM.
that's superb that you've both noticed from my misunderstanding that I've read spring for string, without my saying it!

but how am I to know that the resulting motion won't go beyond their extensions and give a larger amplitude than the existing extension?
0
3 months ago
#6
It's the raison detre of a spring. The force is zero at the unstretched natural length. Shorter it pushes, longer it pulls. Here you have two springs. The center is where the forces cancel.
(Original post by Maths&physics)
brilliant! how did you know I misread the word spring for string?!

"The natural length of a single spring would be the center of the resulting SHM." what do you mean?
0
#7
(Original post by mqb2766)
It's the raison detre of a spring. The force is zero at the unstretched natural length. Shorter it pushes, longer it pulls. Here you have two springs. The center is where the forces cancel.
the centre is where the forces are balanced/equal? but how do I know the amplitude will remain the same as the extension?
0
3 months ago
#8
The initial condition has zero velocity. It is physically impossible to deviate more than this from the center point in the subsequentsmotion. Otherwise you're getting energy for free.
Last edited by mqb2766; 3 months ago
0
#9
(Original post by mqb2766)
The initial condition has zero velocity. It is physically impossible to deviate more than this from the center point in the subsequentsmotion. Otherwise you're getting energy for free.
ok, but the spring on the LHS is compressed (gone beyond its natural length) before it's released, so why wouldnt that effect its subsequent motion - I guess the answer is no, but why?
Last edited by Maths&physics; 3 months ago
0
3 months ago
#10
The first part asked you to show that the motion is SHM, you must have considered both forces or springs acting on the body? From then on, you should not really care about what happens to the spring individually?

(Original post by Maths&physics)
ok, but the string on the LHS is compressed (gone beyond its natural length) before it's released, so why wouldnt that effect its subsequent motion - I guess the answer is no, but why?
0
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