Reference Guide

5-22 Equation Reference
Variable
Description
A
Projected area relative to flow
ar
Centripetal acceleration at r
at
Tangential acceleration at r
Cd
Drag coefficient
E
Energy
F
Force at r or x, or Spring force (Hooke’s Law), or attractive
force (Law of Gravitation), or Drag force (Drag force)
I
Moment of inertia
k
Spring constant
Ki,Kf
Initial and final kinetic energies
m, m1, m2
Mass
N
Rotational speed
Ni, Nf
Initial and final rotational speeds
P
Instantaneous power
Pavg
Average power
r
Radius from rotation axis, or
Separation distance (Law of Gravitation)
t
Time
v
Velocity
vf, v1f, v2f
Final velocity
vi, v1i
Initial velocity
W
Work
x
Displacement
Reference: 3.
Linear Mechanics (4, 1)
Equations:
F m a⋅= Ki
1
2
---
m vi
2
⋅ ⋅=
Kf
1
2
---
m vf
2
⋅ ⋅=
W Kf Ki–=
vf vi a+ t⋅=
P F v⋅=
Pavg
W
t
-----
=
W F x⋅=
Example:
Given: t=10_s, m=50_lb, a=12.5_ft/s^2, vi=0_ft/s.
Solution: vf=125_ft/s, x=625_ft, F=19.4256_lbf, Ki=0_ft ∗ lbf, Kf=12140.9961_ft ∗ lbf, W=12140.9961_ft ∗ lbf,
Pavg=2.2075_hp.