1. General Principles
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2. Objectives
To provide an introduction to the basic quantities and idealizations of mechanics.
To review the principles for applying the SI system of units.
To examine the standard procedures for performing numerical calculations.
To present a general guide for problem solving.
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3. Mechanics: Definition
Branch of physical sciences concerned with the state of rest or motion of bodies subjected to forces.
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4. Engineering Mechanics
Solid Mechanics
Fluid Mechanics
Rigid Bodies
Deformable Bodies
Statics
Dynamics
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5. Rigid Body Mechanics Statics – Bodies at rest
Dynamics – Accelerated motion of bodies
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6. Basic Quantities Length Time Mass Force meter foot second kilogram
slug
Force
newton
pound
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7. Length
Needed to locate the position of a point in space and describe the size of a physical system.
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8. Time
Conceived as a succession of events. Concepts of STATICS are time independent.
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9. Mass
A property of matter by which we can compare the action of one body to another. This property manifests itself as a gravitational attraction between two bodies and provide a qualitative measure of the resistance of matter to a change in velocity.
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10. Force
Generally considered as a push of a pull exerted by one body on another. Interaction occurs when there is direct contact between the bodies. Gravitational, electrical and magnetic forces do not require direct contact. Force is characterized by magnitude, direction and point of application.
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11. Idealizations
Particle - an object having mass but the size is neglected.
Rigid Body - a combination of a large number of particles which remain in a fixed position relative to each other, both before and after the application of a force.
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12. SI Units Modern version of metric system.
Base units are length, time and mass, meter (m), second (s), and kilogram (kg)
Acceleration of gravity:
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13. SI Units Force is derived quantity measured in unit called a newton
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14. Systems of Units Name SI Length Time Mass Force meter (m) second (s)
kilogram
(kg)
newton
(N)
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15. Prefixes for SI units
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16. Dimensional Homogeneity
Each of the terms of an equation must be expressed in the same units.
s = v t + 1/2 a t 2
s is position in meters
v is velocity in m/s
a is acceleration in m/s2
t is time in seconds
[m] = [m/s]  [s] + [m/s2]  [s2] = [m]
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17. Convert 2 km/h to m/s. How many ft/s is this?
SOLUTION:
Since 1 km = 1000 m and 1 h = 3600 s, the conversion
factors are arranged so that a cancellation of units can be applied.
Recall that 1 ft = m
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18. Procedure for Analysis
Read the problem carefully and correlate the actual physical situation with the theory studied.
Draw necessary diagrams and tables.
Apply relevant principles, generally in mathematical form.
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19. Procedure for Analysis
Solve the equations algebraically (without numbers) as far as possible, then obtain a numerical answer.
Be sure to use a consistent set of units.
Report the answer with no more significant figures than the accuracy of the given data.
Decide if answer seems reasonable.
Think about what the problem taught you!
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