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Key Concepts

Mechanics is the science that considers the motion

of bodies under the action of forces.

Statics is the study of motionless systems or

systems that move with a constant velocity.

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Fig. 1.1 Directed line segment

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7/27/2019 Theory Statics Chap1A

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Key Concepts

A particle is a body whose size does not influenceits response to the forces acting on it

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Key Concepts

A rigid body is a body that does not deform under

the action of forces. Generally, the size of a rigidbody influences its response to forces.

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Key Concepts

The acceleration of a particle is proportional to the

net force that acts on the particle and inverselyproportional to the mass of the particle.

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Key Concepts

Every force (action) is accompanied by an equal

and opposite force (reaction).

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Fig. 1.3 Original definition of the meter.

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Key Concepts

Weight is a force, not a mass. The kilogram is a

unit of mass, not a unit of weight.

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Fig. 1.4 Balance-type scale.

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Fig. 1.5 Spring scale: (a) in

a zero-gravity field; (b) on

the moon; (c) on earth.

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Fig. 1.6 A force of 1 N acting on a mass of 1 kg produces an acceleration of 1 m/s2

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Fig. 1.7 The weight of a unit mass equals gunits of force.

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Key Concepts

SI is an absolute system of units. The United

States Customary System is a gravitational systemof units.

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Fig. 1.8 A force of 1 lb acting on a mass of 1 slug produces an

acceleration of 1 ft/s2.

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Key Concepts

Units and dimensions can be manipulated like

algebraic quantities; that is, they can be added,multiplied, divided, combined, or canceled.