Let Air Show Its Muscles
You will need: A balloon, three or four books.
Have you ever noticed a car with a flat tire? The vehicle is no longer horizontal but sags at that end where the air has been released from the tire.
If you could reach the axle of the car immediately above the flat tire, you would probably find your strength insufficient to raise the end of the car at all.
Yet when air is pumped back into the tire the car is gradually lifted. Air pressure can raise the weight of quite heavy trucks in this fashion.
A similar experiment to test the lifting strength of air pressure can be performed with a toy balloon and a few books. Secure three or four books with rubber bands or string and place them on top of a toy balloon. Place the balloon so that the mouthpiece overhangs the edge of the table.
Take a deep breath and blow steadily into the balloon. You will be surprised to see how easily the end of the pile of books is raised into the air. See if you can lift more books than your friend, in this fashion.