- #31
- 7,328
- 2,852
Rather than focus on "forces", it might be better to focus on the
"transfer of momentum [from one object to another]"...
one object gaining momentum ##\Delta \vec p_1\stackrel{Newton2nd}{=} \Delta \vec p_{1\mbox{ from 2}}##
because the other object transferred momentum to it: ##\Delta \vec p_{2\mbox{ from 1}} \stackrel{Newton3rd}{=} - \Delta \vec p_{1\mbox{ from 2}}## .
Yes, it deals with the impulse and the time-integral of the force...
but, as others have tried to emphasize,
it's more than a formula, a "change", or a sign.
It's about what object is applying the force (the source of the force.. source of the momentum-transfer)
and what object is receiving that force (the target of the force.. target of the momentum-transfer).
Think of it as an accounting problem.
"transfer of momentum [from one object to another]"...
one object gaining momentum ##\Delta \vec p_1\stackrel{Newton2nd}{=} \Delta \vec p_{1\mbox{ from 2}}##
because the other object transferred momentum to it: ##\Delta \vec p_{2\mbox{ from 1}} \stackrel{Newton3rd}{=} - \Delta \vec p_{1\mbox{ from 2}}## .
Yes, it deals with the impulse and the time-integral of the force...
but, as others have tried to emphasize,
it's more than a formula, a "change", or a sign.
It's about what object is applying the force (the source of the force.. source of the momentum-transfer)
and what object is receiving that force (the target of the force.. target of the momentum-transfer).
Think of it as an accounting problem.