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TRACTIVE FORCE REQUIREMENTS.
Vehicles require thrust forces, generated at the tires, to initiate and maintain motion. These forces
are usually referred to as tractive forces or the tractive force requirement. If the required tractive
force (F) is broken into components the major components of the resisting forces to motion are
comprised of acceleration forces (Faccel = ma & I forces), Gradeability requirements (Fgrade),
Aerodynamic loads (Faero) and chassis losses (Froll resist ).
F = Faero + Froll resist + Fgrade + Faccel
= (/2) Cd A v2 + Crr m g + %slope m*g + m a
= (/2) Cd A v2 + m g{Crr + % slope + a/g}
in SI units:
A = frontal area (m2) v = velocity (m/s) m = mass (kg)
Crr = coefficient of roll resistance (N/N) usually approx .015
Cd = coefficient of aero drag for most cars .3 - .6
% slope = Rise/Run = Tan of the roadway inclination angle
Steady state force are equal to the summation of Faero + Froll resist + Fgrade
  Faero  Froll resist  Fgrade ss F
Transient forces are primarily comprised of acceleration related forces where a change in velocity
is required. These include the rotational inertia requirements (FI ) and the translational mass
(Fma) requirements, including steady state acceleration.
VEHICLE ENERGY REQUIREMENTS.
The energy consumption of a vehicle is based on the tractive forces required, the mechanical
efficiency of the drive train system, the efficiency of the energy conversion device and the
efficiency of the storage system. Examples of the above might best be demonstrated with the
following.
Storage efficiency:
A flywheel used for energy storage will eventually lose its total energy stored due to
bearing and aerodynamic losses. A storage battery may eventually discharge due to
intrinsic...