Problem with mathematical operations

I am having trouble putting this together on matlab

t=0:0.05:.35
v(t)=sqrt((0.0035*(1440)*9.81)/0.0018)*tanh(sqrt(0.0335*(1440)*9.81*0.0018)/(0.035*2700).*t)

all of that is times t and then tanh(t) I tried to work it out and the book says the result a t=0.35 is 0.5120m/s what am I doing wrong thanks for the help

Answer 1

[the cyclist]

I see one specific problem with your code, and a couple potential ones. To help myself see what's going on, I rewrote your code, using parameters instead of inserting repeated numbers into the equation:

t = 0:0.05:.35;

c1 = 0.0035;
c2 = 0.0335;
c3 = 0.035;

a = 1440;

g = 9.81;

b = 0.0018;
d = 2700;

v = sqrt(c1*a*g/b) * tanh(sqrt(c2*a*g*b)/(c3*d).*t);

Notice that I changed v(t) to just v. You are not making a function here, but instead are calculating values of v. [That was probably giving you a syntax error.]

One thing I notice that I find likely to be an typo on your part is that your equation has the three different values that I called c1, c2, c3. Are any of those typos?

Answer 2

[francis]

its the problem 3.6 of the matlab book pg 87

r=0.2;
vl=(4/3)*pi()*r^3;
t=0:0.05:0.35;
q=sqrt((vl*1440*9.81)/(0.0018))*tanh(sqrt(vl*1440*9.81*0.0018)/(2700*vl).*t)

the problem was to find the volume of the sphere with the radius of 0.2, I got 0.0335 , I have been checking and still got 0.35s 1.832 velocity

[the cyclist]

"the matlab book" isn't very meaningful. (Amazon lists over 4,600 books when you search on MATLAB.)

Can you post a screen shot of the problem?

[francis]

http://s1348.photobucket.com/user/Francisdistefano860/media/photo14_zps44fc8143.jpg.html?sort=3&o=0\

here I couldnt figure out how to do it here, thanks for the help I really appreciated

[the cyclist]

Found it.

You have an error in your units. The radius of the sphere is 0.2 cm, not 0.2 m.

[francis]

thank you so much,that was the last thing I would of had thought