Rolling Car Model  

In this model, students combine friction and drag as opposing forces to look at the effect on a car in motion.

THE MODEL
Vensim Version STELLA Version

[Diagram Level | Equations Level | Graphs ]


Displacement(t) = Displacement(t - dt) + (Rate_of_change_of_Displacement) * dt
INIT Displacement = 0 {m}
Rate_of_change_of_Displacement = Velocity
Velocity(t) = Velocity(t - dt) + (Rate_of_change_of_Velocity) * dt
INIT Velocity = 0 {m/s}
Rate_of_change_of_Velocity = Acceleration
Acceleration = Net_force/mass
acceleration_due_to_gravity = -9.8 {m/s^2}
air_density = 1.2 {kg/m^3}
Applied_force = Engine
coeff_rolling_friction = .015
cross_sect_area = 2 {m^2}
cross_sect_coeff = .5
drag = -0.5*cross_sect_coeff*air_density*cross_sect_area*Velocity^2
Engine = 387 {N}
friction = coeff_rolling_friction*Weight
mass = 1000 {kg}
Net_force = Applied_force+Opposing_force
Opposing_force = drag+friction
Weight = mass*acceleration_due_to_gravity

Time Specs Settings
Range: 0-300 ; dt = 1.0; Integration Method = Euler's

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