INTRODUCTION Today’s objectives: Fundamental concepts Newton laws Units Numerical calculation

WHAT IS MECHANICS?? Either the body or the forces could be large or small. Study of what happens to a particle/body when FORCES are applied to it.

Physics ElectromagnetismOpticsThermodynamics WHERE IS MECHANICS?? Mechanics Rigid Bodies (Things that do not change shape) Statics EnPh130 Dynamics EnPh 131 and Mece 250 Deformable Bodies (Things that do change shape) Fluids IncompressibleCompressible

WHO STARTED IT ALL! Sir Isaac Newton See his biography at: He managed, for the first time, to explain the relation between different physical quantities using: 1.A Mathematical language (calculus) 2.Experimental laws such as:

DYNAMICS Dynamics is the study of the motion of the objects:  Kinematics is the study of the geometry of the motion or how position, velocity and acceleration of a moving object are related. (First part of this course)  Kinetics deals with how motion is caused by the applied forces. (Second part of this course)

1.Particle vs. Rigid Body In Rigid body, we should consider both mass and size Rigid body has both translational and rotational motion In Particle, mass is considered but “size” is neglected Particle has no rotational motion Rule of thumb: a finite body can be considered as a particle as long as the rotation of the body is not important in the resulting motion TWO IMPORTANT IDEALIZATION

2.Concentrated force vs. Distributed force The hydrostatic force of the water behind a dam is distributed over the surface The cable force is a concentrated force or point force since it is applied to a point on the crate. In dynamics of particle we usually deal with point force or concentrated forces TWO IMPORTANT IDEALIZATION

QUANTITIES Basic Quantities: 1.Length, 2.Time 3. Mass m F=ma  velocity, acceleration Force (not independent from the first three)

UNIT SYSTEMS Note: 1.Unit is a part of a physical quantity. Don’t forget to report the units in your calculations and final answers 2.It is worth memorizing some simple unit conversion factors: 1 ft = m, 1 lb = N, 1 slug = kg

NUMERICAL CALCULATIONS (review) Must have dimensional “homogeneity.” Dimensions have to be the same on both sides of the equal sign, (e.g. distance = speed  time.) Be consistent when rounding off. - greater than 5, round up (3528  3530) - smaller than 5, round down (  ) - equal to 5 and zeros in the following digits, then round to the closest even digit (2415  2420 or 2425  Use an appropriate number of significant figures (3 for answers, at least 4 for intermediate calculations).

SAMPLE CONCEPT QUIZ 1. Give the most appropriate reason for using three significant figures in reporting results of typical engineering calculations. A) Historically, slide rulers could not handle more than three significant figures. B) Three significant figures gives better than one-percent accuracy. C) Telephone systems designed by engineers have area codes consisting of three figures. D) Most of the original data used in engineering calculations do not have accuracy better than one percent