New Sharper Views of Apollo Landing Sites
via fine structure
Daily Archives: September 7, 2011
Sounds Like a Teen Horror Flick
The Scale at the Bottom of a Pool
“An Olympic-sized swimming pool is filled with 660,000 US gallons of water. An imaginary scale under the pool reads 5,511,556 pounds — the weight of the water. Now a 12,000 pound, 5 foot wide spherical wrecking ball is lowered halfway into the water by a crane. What does the scale read?”
Fulfilling Their Expectations
The Preconception Eliciting Tennis Ball
While holding the ball near the ceiling, I ask, “When the ball is at its peak, what is its velocity?” (They confidently say “zero!”)
I now expose their preconception by immediately asking, “What is its acceleration?” (The answers are split between “9.8 m/s/s” and “zero!” depending on the class) I keep the ball near the ceiling and ask one of the students who enthusiastically answered “zero!”, “If its acceleration is zero and its velocity is zero, what would happen to the ball?” After some thought, the student realizes that the ball wouldn’t fall. I then release the ball and it sticks to the ceiling.