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Doc Al
Sep20-11, 10:00 AM
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Quote Quote by Studiot View Post
The first is the original inspiration from Professor Den Hartog. I have ringed the paragraph where he clearly and explicitly states that the third law reaction is a result of inertia. However he does not elaborate as to how this might arise as he has other fish to fry.
I'd say that despite the non-standard terminology, that first extract is clearly talking about 'reaction' forces. These are 'real' forces due to the interaction of two different bodies.

To see how this might arise the second extract is from Walker.
This makes the statement Doc Al thinks is in conflict with Den Hartog but to see that it is not, look at the diagram first.
That second extract, despite its failure to make explicit the fact that it is using a non-inertial frame of reference, seems clearly to be talking about inertial forces. Note that the applied force and the inertial force both act on the mass in question. (Not so in the first extract.)

Apples and oranges, I'm afraid.