Is this Simple Harmonic Motion?

  • #1

Summary:

a question about if this particular object follows SHM?

Main Question or Discussion Point

I've been going to the theme park almost every year-and this year in my Physics class we are learning mechanics, more specifically Simple Harmonic Motion.
My teacher told us that for an object to have 'Simple Harmonic Motion' it must have oscillatory motion (like a pendulum going back and forth).

Here is the link to a short video of the ride at the theme park I go to: (just skip the video to about the 1/2 way mark).

I was wondering if this follows SHM?

I'm a bit confused because the swinging part of the ride gets successively higher as the ride proceeds.

And I'm wondering if the rotating part of the ride affects the SHM? because in a 'normal pendulum demo', the bob doesn't rotate/spin as it oscillates.

Thank you for reading :)
 

Answers and Replies

  • #2
Orodruin
Staff Emeritus
Science Advisor
Homework Helper
Insights Author
Gold Member
16,810
6,600
No, this is not simple harmonic motion and there are many reasons for it.
  1. As you have noticed, energy is clearly being put into the motion as the amplitude increases.
  2. A pendulum is generally not undergoing SHM. If your teacher claims this he is wrong. For SHM it is not sufficient for the motion to be periodic and the motion of a pendulum is only well approximated by SHM if the amplitude is very small. This is clearly not the case here.
  3. Regarding the rotation, it is a bit unclear which part of the ride you are asking about the SHM for. It is clearly not the case that the people on the ride are in SHM.
 
  • Like
Likes solarmidnightrose
  • #3
sophiecentaur
Science Advisor
Gold Member
24,426
4,403
we are learning mechanics, more specifically Simple Harmonic Motion.
Most examples in real life may be Harmonic Motion - just not Simple.
SHM can be described by a basic sine wave in time. Even the familiar pendulum is not exactly SHM. The nearest we get to mechanical SHM is a mass bouncing on a good, uniform spring. That relies of good old Hooke's Law which tells us that a spring follows a linear relationship between force and extension.
 
  • #4
No, this is not simple harmonic motion and there are many reasons for it.
  1. As you have noticed, energy is clearly being put into the motion as the amplitude increases.
  2. A pendulum is generally not undergoing SHM. If your teacher claims this he is wrong. For SHM it is not sufficient for the motion to be periodic and the motion of a pendulum is only well approximated by SHM if the amplitude is very small. This is clearly not the case here.
  3. Regarding the rotation, it is a bit unclear which part of the ride you are asking about the SHM for. It is clearly not the case that the people on the ride are in SHM.
Thank you for replying!
So, as this is not SHM, is it still possible to do calculations related to SHM?

things such as:
  • amplitude
  • frequency
  • period
  • angular velocity/acceleration
 
  • #5
Most examples in real life may be Harmonic Motion - just not Simple.
SHM can be described by a basic sine wave in time. Even the familiar pendulum is not exactly SHM. The nearest we get to mechanical SHM is a mass bouncing on a good, uniform spring. That relies of good old Hooke's Law which tells us that a spring follows a linear relationship between force and extension.
Thank you for making this clear :)
 
  • #6
sophiecentaur
Science Advisor
Gold Member
24,426
4,403
So, as this is not SHM, is it still possible to do calculations related to SHM?
I think this is a matter of degree. We describe a Radio Signal in terms of its centre / main frequency which is treating it as a sinusoidal variation of volts. But then we acknowledge that it carries information which implies that it takes up a significant bandwidth. It is not a sine wave BUT that approximation works fine for antenna and amplifier design.
Basically we are in the real world and SHM is a working approximation in many cases. But there is always a caveat.
 

Related Threads on Is this Simple Harmonic Motion?

Replies
6
Views
457
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
4
Views
2K
  • Last Post
Replies
2
Views
323
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
8
Views
780
Replies
13
Views
2K
Replies
3
Views
2K
Top