# Need help with spring launcher please

psp101

## Homework Statement

hi this is my first time posting here but I'm been on the forum a lot just looking for help on this assignment I have

I need to make a spring laucher that's 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

## Homework 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

## The Attempt at a Solution

no idea how to solve this

psp101
nm about the picture I can't post a image until 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
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.

Homework Helper
Welcome to PF!

Hi psp101! Welcome to PF!
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
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.