How does Newton's 3rd law apply in this case?

  • #1
WhatsApp Image 2018-10-19 at 3.09.04 PM.jpeg

Homework Statement



It is clear that SOMETHING exerts a force on the conducting wire in a downwards direction.
By Newton's 3rd law, the (field of) this conducting wire also exerts a force on something.

Homework Equations



Could the magnet be said to move upwards (and hence reading decrease) due to an equal opposite reaction force?

The Attempt at a Solution



I'm not sure which direction the "reaction force" acts in. I've also read a bunch about conservation of momentum and having to consider field velocity, but is there any way to answer this question without talking about all that? Thanks!
 

Attachments

  • WhatsApp Image 2018-10-19 at 3.09.04 PM.jpeg
    WhatsApp Image 2018-10-19 at 3.09.04 PM.jpeg
    32.2 KB · Views: 462

Answers and Replies

  • #2
Orodruin
Staff Emeritus
Science Advisor
Homework Helper
Insights Author
Gold Member
16,933
6,739
Could the magnet be said to move upwards (and hence reading decrease)
These are not the same thing. Something can be stationary and still have different forces acting upon it.

I'm not sure which direction the "reaction force" acts in.
What does Newton's third law tell you?

I've also read a bunch about conservation of momentum and having to consider field velocity, but is there any way to answer this question without talking about all that?
This is a static situation. There is no reason whatsoever to involve velocities.
 
  • #3
Hmm so would it be conceptually accurate to phrase the problem this way:

Force 1: force of magnet on conductor (downwards)
Force 2: force of conductor on magnet (upwards) ?
 
  • #4
Orodruin
Staff Emeritus
Science Advisor
Homework Helper
Insights Author
Gold Member
16,933
6,739
Hmm so would it be conceptually accurate to phrase the problem this way:

Force 1: force of magnet on conductor (downwards)
Force 2: force of conductor on magnet (upwards) ?
Yes.
 
  • #6
CWatters
Science Advisor
Homework Helper
Gold Member
10,533
2,298
I agree.

Your working should mention Fleming's left hand rule for motors.
 
  • #7
I agree.

Your working should mention Fleming's left hand rule for motors.
Awesome, thank you!
 

Related Threads on How does Newton's 3rd law apply in this case?

  • Last Post
Replies
10
Views
3K
Replies
1
Views
903
Replies
2
Views
1K
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
4
Views
2K
  • Last Post
Replies
6
Views
1K
  • Last Post
Replies
11
Views
2K
  • Last Post
Replies
10
Views
2K
  • Last Post
Replies
1
Views
973
Top