
#1
Oct711, 04:03 AM

P: 10

An object of mass m falls from rest at a point near the earth's surface. If the air resistance is proportional to the velocity v^2, the differential equation for the velocity as a function of time is given by:
m*dv/dt = mg  cv^2 a) Derive the exact solution done this part, and i got v = sqrt(m*g/c)*tanh(t*sqrt(g*c/m)) b) For the given paraments g = 9.81 m/s^2. m = 68.1 kg and c = 1.5 kg/m. plot the exact solution and the numerical solution v(t) obtained from the 4th order predictorcorrector runge kutta methods using an interval of dt = 0.25 seconds in the domain of 0<t<6 i'm having trouble coding the runge kutta method with all the k1, k2, k3 and k4.. I really need help with this. Thanks 



#2
Oct711, 05:58 AM

P: 330

Matlab already has a builtin RungeKutta solver, probabaly ode45. So I think you need not have to worry about those k_{i}'s.



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