How do you make an object disappear when it collides with another object?

local Wall = script.Parent

Wall.Touched:Connect(function(hit)
      if hit.Name == "Ball" then
         hit:Destroy()
      end
end)

You would have to use the touched event to detect when the ball hits the back wall. You might need to use a module script but idk much about them. Here's the code:

local ball = script.Parent
    ball.Touched:Connect(function (hit)
        if hit.Name == "Part name" then
            ball.Transparency == 1
        end
    end)

Note: Each ball needs to have this script in it for this to work. The ball will only disappear when hitting the floor so not if it hits anything else like a player. If your back wall is made up of multiple parts you need to change hit.Name to hit.Parent.Name

Hope this helps!

Ok So Here The Step:

1. Make A Floor

Make a floor that will destroy the ball, name it "Floor".

2. Make A Script

Make a Script and place it inside the "Floor".

Copy and Paste This Script:

local Floor = script.Parent

Floor.Touched:Connect(function(Hit) -- Detect If Something Touch The Floor
      if Hit.Name == "Balls" then -- Replace "Balls" with the name of your Falling Ball.
         Hit:Destroy() -- Destroy The Ball
      end
end)

Explanation

1. local Floor = script.Parent is the Floor

2. Floor.Touched will detect if something Touched the Floor, then will :Connect() it to a function

3. if Hit.Name == "Balls" if the Hit name was "Balls", then...

4. Hit:Destroy() It will :Destroy() the Hit

Hope It Helps!

This script detects when the ball touches another object and checks if it is the correct object.

local Part1 = game.Workspace.Part1 --Whatever the ball is
local Part2 = game.Workspace.Part2 --Whatever the ball is hitting

Part1.Touched:Connect(function(p) --Connected function

    if p == Part2 then --Check if its the right part

        --Code here

    end

end)