Finding the terminal velocity of a model rocket from a list of velocities

[LT72884]

Good, so rewrite it. After you have done that set the acceleration to 0, and solve the resulting equation.

Vt = sqrt(-mg/k)

 

[erobz]

Vt = sqrt(-mg/k)

Are you going to get a real result when you take the square root of that? What equation did you algebraically manipulate to get that result?

 

[LT72884]

Are you going to get a real result when you take the square root of that?

nope, it will be imaginary. i am trying to see which way to solve this.

 

[erobz]

nope, it will be imaginary. i am trying to see which way to solve this.

You didn't solve the equation you wrote??? Pick a direction as positive. Label all forces on rocket relative to that chosen direction. Please list that full equation in your next reply.

 

[LT72884]

You didn't solve the equation you wrote??? Pick a direction as positive. Label all forces on rocket relative to that chosen direction. Please list that full equation in your next reply.

i solved for v which then becomes imaginary due to the negative in the sqrt. so i need to solve for v a different way. ok, iw ill write soon

 

[erobz]

i solved for v which then becomes imaginary due to the negative in the sqrt. so i need to solve for v a different way. ok, iw ill write soon

you clearly solved a different equation from what you were writing ( as far as the directions of the forces go), or you made a trivial algebra mistake.

 

[LT72884]

with m(dv/dt) = mg-kv^2
and if i set dv/dt = a = 0
therefore 0=mg-kv^2
then solve for v using the correct signs
kv^2 = mg
v^2=(mg)/k
v=sqrt(mg/k)
if i am misunderstanding you, im sorry haha:)

 

[erobz]

with m(dv/dt) = mg-kv^2
and if i set dv/dt = a = 0
therefore 0=mg-kv^2
then solve for v using the correct signs
kv^2 = mg
v^2=(mg)/k
v=sqrt(mg/k)
if i am misunderstanding you, im sorry haha:)

Ok, that’s better. So what did you get for the terminal velocity?

 

[LT72884]

Ok, that’s better. So what did you get for the terminal velocity?

just making sure but K is the same as Beta right?
give me a few moments to get this calculated. might be about an hour or so. had something come up that is very important

 

[erobz]

just making sure but K is the same as Beta right?
give me a few moments to get this calculated. might be about an hour or so. had something come up that is very important

Yeah. k is β. No hurry.

 

[LT72884]

Yeah. k is β. No hurry.

average terminal velocity is 234.68. IF this was free fall... but we know its not

 

[LT72884]

average terminal velocity is 234.68. IF this was free fall... but we know its not

thanks for all the help. I really do appreciate it a lot. Our actual project is to design an active drag system for our rocket. This ADS will be used to slow the rocket down to achieve as close to 10,000 feet as possible. so far our design is pretty cool.

 

[erobz]

thanks for all the help. I really do appreciate it a lot. Our actual project is to design an active drag system for our rocket. This ADS will be used to slow the rocket down to achieve as close to 10,000 feet as possible. so far our design is pretty cool.

Well, best of luck out there, and have fun with the rest of it!

 

[LT72884]

Well, best of luck out there, and have fun with the rest of it!

thank you very much my friend:) your an excellent teacher

 

[erobz]

Just an amateur, but thanks for the compliment.

 

[LT72884]

well, better than me haha. i taught high school math for a few years, but physics was never my strong suite haha.