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INTRODUCTION

ENGINEERING AND MECHANICS

MECHANICS - the study of forces and their effects

STATICS - the study of objects in equilibrium

DYNAMICS - the study of objects in motion

LEARNING MECHANICS

The main goal - understand the principles well enough to apply them to new situations

Problem Solving:

- Identify the information that is given and the information/answer to determine

- Develop the strategy – identify the principles and equations to apply, and draw diagrams if possible

- Try to predict the answer

- Solve the equations and interpret results (and compare them with the prediction)

Engineering Applications

Essential aspects of engineering:

- Design (choose values of parameters to satisfy stated design criteria)

- Safety (choose values of parameters to satisfy stated safety requirements)

Fundamental Concepts

Numbers

Engineering measurements, calculations and results are expressed in numbers.

Space and Time

|Space |– |geometric region occupied by bodies whose positions are described by linear and angular measurements relative to a coordinate system. |

|Time |– |measure of the succession of events; basic quantity in dynamics, not directly involved in statics. |

|Mass |– |measure of the inertia of a body (resistance to a change of a velocity), or the quantity of matter in a body; also, the property of every body by which it experiences |

| | |mutual attraction to other bodies. |

|Force |– |action of one body to another; tends to move a body in the direction of its action; vector quantity. |

|Particle |– |body of negligible dimensions (may be analyzed as a point mass) |

|Rigid body |– |relative movements between its part are negligible for the purpose in hand |

Newton’s Laws

|I |– |A particle remains at rest or continues to move in a straight line with uniform velocity if there is no unbalanced force acting on it. |

|II |– |The acceleration of a particle is proportional to the resultant force acting on it and is in the direction of this force. |

|III |– |The forces of action and reaction between interacting bodies are equal in magnitude, collinear, and opposite in direction. |

UNITS

| |Dimensional |SI Units |U.S. Customary Units |

|Quantity |Symbol |unit |symbol |unit |symbol |

| Mass |M |Base units|kilogram |kg | |slug |- |

| Length |L | |meter |m |Base units|foot |ft |

| Time |T | |second |s | |second |s |

| Force |F | |newton |N | |pound |lb |

Derived units: 1 N = 1 kg-m/s2 SI Units

1 slug = 1 lb-s2/ft U.S. Customary Units

The common prefixes used in SI units and the multiples they represent

|Prefix |Abbreviation |Multiple |

| pico- |p |10-12 |

| nano- |n |10-9 |

| micro- |μ |10-6 |

| mili- |m |10-3 |

| kilo- |k |103 |

| mega- |M |106 |

| giga- |G |109 |

| tera- |T |1012 |

Angular Units

|Quantity |unit |symbol |unit |symbol |

|Angle |radian |rad |degree |( or deg |

Conversion of Units

|Length |1 in |= |25.4 mm |

| |1 ft |= |12 in |

| | |= |0.3048 m |

| |1 mi |= |5280 ft |

| | |= |1609 m |

| |1 m |= |3.281 ft |

| |1 km |= |0.6214 mi |

|Time |1 min |= |60 s |

| |1 hr |= |60 min |

| |1 day |= |24 hr |

|Mass |1 slug |= |14.59 kg |

| |1 kg |= |0.0685 slug |

|Force |1 lb |= |4.448 N |

| |1 N |= |0.2248 lb |

|Angle |2 π rad |= |360( |

| |1 rad |= |57.3( |

| |1( |= |0.01745 rad |

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SI and U.S. Customary units

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