science in daily usage

India
May 24, 2008 3:46am CST
I AM unable to explain my child ,who is in 5th standard , that when he is playing with a balloon of air filled, he is pushing the balloon up ,it goes up and coming down again and again. After some time the balloon's mouth was suddenly open and the air is come out of it.At the time of air coming out , that balloon went up with a natural force. My son is asking that previously that balloon was coming down is now immediately raised or pushed up suddenly when the air is evacauted from the balloon ? I cannot explain him correctly . So, if any body can help me to explain this event scientifically , I am grateful to her or him ?
1 response
@Elixiress (3893)
24 May 08
The force acting down on the balloon is gravity, which pushes the balloon down to the floor, but when the air comes out of the balloon or any other force acts in the opposite direction to gravity it will propel it upwards for a period of time, this is called upthrust, but these forces balance themselves out and the balloon stops moving and then the upthrust is not as strong anymore and gravity is stronger so the balloon falls again.