2-Particle Interactions 1 2 f 21 f 12 Sun : earth Atom : atom
3-Particle Interactions 1 2 f 21 f 13 3 f 12 f 31 f 23 f 32 F3F3 F1F1 F2F2
Many-Particle Interactions 1 2 f 21 f 13 3 f 12 f 31 f 23 f 32 F3F3 F1F1 F2F2 Summation of the above equation gives Newton’s 3 rd law Therefore: For an N particles system, in equilibrium Newton’s 1st law
Free-Body-Diagram Isolate the body in question with the representation of all external forces acting on it.
Remove Spike from Timber It is desired to remove the spike from the timber by applying force along its horizontal axis. An obstruction A prevents direct access, so that two forces, one is 1.6kN and the other P, are applied by cables as shown. Compute the magnitude of P necessary to ensure axial tension T along the spike. Also find T.
Remove Spike from Timber T Horizontal: Vertical:
Knot in Static Equilibrium? Mass: m F1F1 F2F2 Horizontal: Vertical:
When strings are almost straight horizontally when Mass: m F1F1 F2F2