- #1

Redfire66

- 36

- 0

## Homework Statement

I'm building a tennis ball launcher (as most people did) and I barely have some calculations done. I already have a measurement for my project (i.e. an angle and such), a k value for my string and a distance that it should travel horizontally. Theoretically, I'm supposed to calculate the velocity it takes the ball to travel the distance horizontally and a stretch distance (x) for my string; I'm not given a maximum height (but it should be above 1m), or time but I do have an initial height where the ball is launched (which is the height of my launcher) - there's quite a bit of missing variables without actually simulating it (since it's required that I calculate before I simulate)

## Homework Equations

Dx=vtcosθ

Fg=kx

E=E

Dy=vtsinθ

V=vcosθ or sinθ depending on direction

(I might be missing some but I suppose you'd get the idea)

## The Attempt at a Solution

Determined the k value by determining the force (mg) and relating to the F=kx equation

I've tried to do Et=Et

But I end up getting stuck with

E(at launch) = E (when pulled back)

mgh + 1/2mv^2 = 1/2kx^2 + mgh

since the heights are different, and since I don't know how far back I stretch it (x), then I won't be able to determine how high it is (for the mgh on the second half); maybe I did it wrong or used the wrong method, but that's how I seem to think I should do it

I'm still thinking it through how I'm supposed to attempt this, and seems sort of difficult without being given more variables