# Engineering Mechanics Lecture 2

## Presentation on theme: "Engineering Mechanics Lecture 2"— Presentation transcript:

Engineering Mechanics Lecture 2
5/10, Friday 3-4am

2-Particle Interactions
Sun : earth f21 Atom : atom f12 2 1

3-Particle Interactions
F3 3 f32 f23 f31 2 F2 f13 f21 F1 f12 1

Many-Particle Interactions
For an N particles system, in equilibrium Newton’s 1st law F3 3 Summation of the above equation gives f32 f23 f31 2 F2 f13 Newton’s 3rd law f21 F1 f12 1 Therefore:

Free-Body-Diagram Isolate the body in question with the representation of all external forces acting on it.

Problem 1

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
Vertical: Horizontal:

Problem 2

Knot in Static Equilibrium?
F1 F2 Horizontal: a b Vertical: Mass: m

When strings are almost straight horizontally
F1 F2 a b when Mass: m