If you\'ve ever played with an inflated ball of any type while swimming, you\'ve
ID: 1786992 • Letter: I
Question
If you've ever played with an inflated ball of any type while swimming, you've probably noticed that if a ball is already floating on the surface of the water, it's easy to push it down a few centimeters. But then it's harder to push it the next few cm down, and so on, until the ball is completely submerged – the last few cm are the hardest! a) Explain why you have to push down more and more strongly on the ball the closer it gets to being completely submerged. 1-2 sentences, no equations or math. b) Suppose, once the ball is completely submerged, you hold it there for a while, then push it all the way to the bottom of the pool. Does it take more force to hold it at the bottom of the pool than to hold it just beneath the surface? Explain in a few sentences.
Explanation / Answer
But then it's harder to push it the next few cm down, and so on, until the ball is completely submerged- because as you push the ball down its volume in the water increases as a result of which buoyant force on it increases. Buoyant force has upward direction and thus water pushes the ball upward due to which you have to push down more and more strongly on the ball the closer it gets to being completely.
When the ball I submerged in the water beneath the surface are gravity downward, buoyant force upward and applied force downward. These forces are same when the ball is at the bottom. Hence force to hold the ball at the bottom is same force to hold the ball at just beneath the surface.