Two functions to test for collisions between rectangles and circles without needing physics.

collisions.lua

-- rectangle based
local function hasCollided(obj1, obj2)
    if obj1 == nil then
        return false
    end
    if obj2 == nil then
        return false
    end
    local left = obj1.contentBounds.xMin <= obj2.contentBounds.xMin and obj1.contentBounds.xMax >= obj2.contentBounds.xMin
    local right = obj1.contentBounds.xMin >= obj2.contentBounds.xMin and obj1.contentBounds.xMin <= obj2.contentBounds.xMax
    local up = obj1.contentBounds.yMin <= obj2.contentBounds.yMin and obj1.contentBounds.yMax >= obj2.contentBounds.yMin
    local down = obj1.contentBounds.yMin >= obj2.contentBounds.yMin and obj1.contentBounds.yMin <= obj2.contentBounds.yMax
    return (left or right) and (up or down)
end
 
-- circle based
local function hasCollidedCircle(obj1, obj2)
    if obj1 == nil then
        return false
    end
    if obj2 == nil then
        return false
    end
    local sqrt = math.sqrt
 
    local dx =  obj1.x - obj2.x;
    local dy =  obj1.y - obj2.y;
 
    local distance = sqrt(dx*dx + dy*dy);
    local objectSize = (obj2.contentWidth/2) + (obj1.contentWidth/2)
    if distance < objectSize then
        return true
    end
    return false
end