Topic 2 Lesson 2
Units and dimensions, systems of units, dimensional homogeneity
Mass and Weight
The Slug as a Unit of Mass
The slug is an alternative unit of mass in the American Engineering
System of units.
A force of one pound-force applied to a mass of one slug will result
in an acceleration of one foot per second squared.
Mass/weight relationship
Newton's Second Law
Relationship between Mass and Weight
Weight = Mass x Acceleration of gravity / gc
W = mg/gc
The weight of a 1.0 kg mass is 9.8 Newtons.
The weight of a 1.0 lbm is 1.0 lbf.
Newton's Second Law
The Relationship between g and gc
g is the gravitational acceleration.
- It has a value of 9.81 m/s2 and 32.174 ft/s2
at sea level and 45° latitude.
- Its value changes slightly as you change elevation on Earth.
- Its value could change dramatically if you traveled to a different
planet.
gc is a constant conversion factor.
- It has a defined value of 1 kg·m/s2 per Newton and
32.174 lbm·ft/s2 per lbf.
- Its value does not change as you change elevation on Earth.
- Its value would not change if you traveled to a different planet.
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