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Need help with spring launcher please

by psp101
Tags: launcher, spring
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psp101
#1
May24-08, 02:50 PM
P: 8
1. The problem statement, all variables and given/known data
hi this is my first time posting here but i'm been on the forum alot just looking for help on this assignment I have

I need to make a spring laucher thats able to change angles and distance
heres an example of my lancher

A spring is launched to a box The target is at a certain distance and height. The question is how do I find the amount I need to strech the spring to get it into the air. bonus how do I add air friction to the equation becaue it obviously makes a diffence

2. Relevant equations
heres given
my spring constant
distance between spring and box
hight of box
angle since its determine by the user

F=kx

x=v0cost

v=v0sin0t+1/2gt

3. The attempt at a solution

no idea how to solve this
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psp101
#2
May24-08, 02:52 PM
P: 8
nm about the picture I cant post a image untill I have 15 posts but its simply an L shaped design with a protractor on its side and a ruler on the top where the spring is lanched
Texag
#3
May24-08, 06:02 PM
P: 19
This may help: Use the formulas for the amount of potential energy in the spring at a certain distance, then equate that with the kinetic energy of the spring once it has left, this will give you the velocity related to the stretch in the spring.

tiny-tim
#4
May24-08, 07:18 PM
Sci Advisor
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P: 26,148
Smile Need help with spring launcher please

Hi psp101! Welcome to PF!
Quote Quote by psp101 View Post
v=v0sin0t+1/2gt
No you mean y = v0sin0t - 1/2gt^2.

And you need to find the other value of t (other than 0, that is) for which y = 0.

Then you can use the x formula.

Is this a practical experiment, so you have to make a real launcher?

If so, how are you going to get the spring to go straight?

Springs are meant to be bendy, and they'll bend sideways as well as up-and-down.

Won't you need something like a long tube?

As to air resistance, I would expect a spring would be horribly un-aerodynamic.

They don't build aeroplanes spring-shaped, do they (oh except maybe the Boing 911! )?
psp101
#5
May25-08, 08:59 AM
P: 8
lol thanks for the help actually the spring is very straght all I need to do is strech it a certian amount with the ruler to meause it to get it across a distance.the only problem before was that I did'nt know how to find that amount I need to strech it to.

I already built the design but I noice the equation is slighty off I just guessed its because of air friction.


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