# Thread: Matlab problems, chapter 11

1. ## Matlab problems, chapter 11

Can anyone help me with 2 Gilat problems?

g354x17 and g356x25

In g354x17, there is a typo. Instead of finding k, we're supposed to find A. Also the function is supposed to be y=sin(pi*x/15).

Thanks to anyone who helps!
In the mean time I will be trying them until I get them but matlab's difficult :-/

Thanks!
LCuba

2. Originally Posted by LCuba
Can anyone help me with 2 Gilat problems?

g354x17 and g356x25

In g354x17, there is a typo. Instead of finding k, we're supposed to find A. Also the function is supposed to be y=sin(pi*x/15).

Thanks to anyone who helps!
In the mean time I will be trying them until I get them but matlab's difficult :-/

Thanks!
LCuba
Try posting the problems not just the page and question number.

CB

3. ## g356x25 problem

Okay, thank you.

both of the problems have pictures associated with them, but g356x25 is solvable without the picture.

g356x25

Damped free vibrations can be modeled by considering a block of mass m that is attached to a spring and a dashpot. From newton's second law of motion, the displacement x of the mass as a function of time can be determined by solving the differential equation:

m*((d^2)x)/(d(t^2)) + c*(dx/dt) + kx = 0

where k is the spring constant, and c is the damping coefficient of the dashpot. If the mass is displaced from its equilibrium position and then released, it will start oscillating back and forth. The nature of teh oscillations depends on teh size of the mass and the values of k and c.

For the system shown in the figure (not shown), m = 10kg, and k = 28 N/m. At time t = 0 the mass is displaced to x = 0.18 m, and then released from rest. Derive expressions for teh displacement x and the velocity v of the mass, as a function of time. Consider the following two cases:

a) c = 3 N-s/m
b) c = 50 N-s/m

For each case, plot the position x and the velocity v vs. time (two plots on one page). For case (a) take 1<= t <= 20 s, and for case (b) take 0 <= t <= 10 s.