 Modeling of problem  Newton’s Law of Motion  Law of Gravitation  Units  Vectors General Principles

Problem Solving Strategy: Physical Model: –Transformation of actual problem into simpler Assumptions –Using Free Body Diagram: FBD Mathematical Model: –Newton’s Law: F=0 and M o =0 (coord. System) Set of equations to be solved Solution of Equations: –Computational Tools: Maple, Matlab, Prog. Interpretation Results: Does answ. Makes sense?

Law #1: Body is in Equilibrium Body will remain at rest or continue to move with same speed (accel.=0) and direction unless unbalance force is acted on body or particle. Newton’s Laws of Motion

Newton’s Law of Motion Law #2: Non-equilibrium Change of motion of a body is proportional to the next force imposed on the body and is in direction of net force.

Newton’s Law of Motion Law #3: Action & Reaction If one body exerts a force on a second body, then second body exerts a force on the first body that is equal in magnitude, opposite in direction and collinear (same line of action).

Any two bodies are attracted to each other with a force whose magnitude is proportional to the product of their gravitational masses and inversely proportional to the square of the distance between them. Law#4: Law of Gravitation M m r F F

(1)If an object has a mass m=50Kg find the weight of object at surface of earth, moon and sun? G = 66.73x (m 3 /Kg/s 2 ) Universal gravitational const. Given: –Mass of earth= 5.976x10 24 Kg –Mass of moon= 7.35x10 22 Kg –Mass of sun=1.99x10 30 Kg –Radius of earth=6.371x10 6 m –Radius of Moon: 1.738x10^6 m –Radius of Sun: 6.96x10^8 m Activity 1: Weight

Weight & Mass: Weight: where: and on earth surface: g= 9.807m/s 2 (SI) or g= ft/s 2 (US) Mass:

Tables 1.6 and 1.7 in book Units

Percent Error A = Value to be Compared B = Reference Value % Error = (A-B)/B (100%)