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Chapter_2 - Basic_Quantities

# Chapter_2 - Basic_Quantities - Chapter 2 Basic Quantities...

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Chapter 2 – Basic Quantities The basic quantities we use in our discussion of propulsion are called units. We have talked about force, mass, and acceleration. There are three basic units from which all other units are derived, mass distance, and time. We can define them both in the English system and the metric system. Metric units are much easier, but in the United States, the metric system has not been adopted in the field of aerospace except at NASA. We shall use both. The three basic units are: English Metric mass slug kilogram distance foot meter time second second Other common units are: speed change in distance time ft/sec (fps) m s area (L x W for rectangle) square feet (ft 2 ) m 2 acceleration change in vel time ft/s s (fts -2 ) m/s 2 Derived units are: force (from Newton's law F = ma) 2 slug ft lbf 5 Newton (N) 2 kg m 5 pressure force area 2 2 lbf lbf or (psi) ft in 2 N Pa = m A force can be thought of as a push or pull on an object. It can be balanced or unbalanced. For example, the book lying motionless on the table experiences a force downward called the gravitational force. It has magnitude, weight, and it has direction, downwards. The fundamental theory we will use in our study of the propulsion are Newtons (three) Laws of Motion. Newtons First Law – A body at rest will remain at rest and a body in motion will remain in

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Chapter_2 - Basic_Quantities - Chapter 2 Basic Quantities...

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