collision function not running - lua

Question

I created 3 balloons(only need 3) and each of them contains a specific word and one of the words is the right answer. I shoot a ball from the cannon and hit the balloons. Assume the balloon 3 holds the balloonText3 which is the right answer, if i hit it the ball and the text disappears. For some reason, the ballCollision(event) doesn't run, i used print statement to confirm it. Whats wrong here?
local cannonBalls = display.newGroup()
...
local shot = function(event)
if(event.phase == 'ended') then
Runtime:removeEventListener('enterFrame', charge)
cannon.isVisible = true
cannon.rotation = 0
cannonBall = display.newImage('cannon ball.png', 84, 220)
physics.addBody(cannonBall, {density = 1, friction = 0, bounce = 0})
cannonBalls:insert(cannonBall)
print ('shot')
-- Shoot cannon ball
cannonBall:applyLinearImpulse(3, impulse, cannonBall.x, cannonBall.y )
--Collision listener
print('event listener')
cannonBall:addEventListener ('collision', ballCollision)
end
end
function ballCollision(event)
if (event.other.name =='balloon3') then
scene.updateScore()
print('Ball is colliding')
timer.performWithDelay(1, e.target.removeSelf, e.target)
timer.performWithDelay(1, e.other.removeSelf, e.target)
balloonText3.isVisible = false
audio.play(pop)
end
end
function scene:createScene(event)
local group = self.view
...
local balloon1 = display.newImage ('balloon_fat_red.png', 495, 60)
local balloon2 = display.newImage ('balloon_fat_red.png', 495, 115)
local balloon3 = display.newImage ('balloon_fat_red.png', 495, 160)
group:insert(balloon1)
group:insert(balloon2)
group:insert(balloon3)
physics.addBody(balloon1)
physics.addBody(balloon2)
physics.addBody(balloon3)
balloon1.bodyType = 'static'
balloon2.bodyType = 'static'
balloon3.bodyType = 'static'
table.insert(balloons, balloon1)
table.insert(balloons, balloon2)
table.insert(balloons, balloon3)
local balloonText1 = display.newText('\227\129\130', 495, 60)
balloonText1:setFillColor( 1,1, 0 )
local balloonText2 = display.newText('\227\129\132', 495, 115)
balloonText2:setFillColor( 1,1, 0 )
local balloonText3 = display.newText('\227\129\134', 495, 160)
balloonText3:setFillColor( 1,1, 0 )
group:insert(balloonText1)
group:insert(balloonText2)
group:insert(balloonText3)
end

Answer 1

I'm going to assume that you put the print statement in the if block of ballCollision, because I can't see anything else wrong with the listener registration. Also, I don't see anywhere in the code where you set the name attribute of the balloon object. So either
add balloon3.name = "balloon3" (and similarly for 1 and 2) after setting bodyType,
or (probably simpler)
use if event.other == balloons[3] then ... in the collision handler. You don't need parentheses around the condition in Lua.