Physics and other lessons

My son has several big tests coming up, so Saturday night’s activity was to have a jovial study session.  Isn’t that what every family does for fun?  The main entertainment value came from recognizing how little this Mom and her Youngest Daughter knew about physics.

Most physics problems involve moving objects.  The first problem we were given was this:  A plane flies 200 km due West from City A to City B.  Then it flies 300 km 30 degrees north of west from City B to City C.  Along a straight-line distance, how far is City A from City C?  

My son said it would be much easier to solve if I drew a picture.  So I did, but I immediately admitted defeat because the points did not form a right triangle. Instead I drew a picture of people waiting in line at the airport, because waiting in line does not involve moving objects, but stationary people, and therefore no physics problem to solve.

As you can see, the solution does involve forming a right triangle eventually.  I will leave it to you people who remember trigonometry to find the solution on your own.  

Next question.  If a body is moved from sea level to the top of a mountain, what changes: its mass, its weight, or both?  After some discussion of what “body” means in physics class (it means “an object” not “a dead human body”), we determined that the weight changes, because the body is further away from the earth’s center of gravity, but the mass does not change. 

Then came the clincher.  He asked, “What metric units do we use to measure weight?”  Youngest Daughter said, “Grams.”  No, that measures mass.  She said, “Pounds.”  Nope, that’s mass in the English system.  Folks, you will never believe this, but the answer is that weight is measured in newtons!  I thought the only thing measured that way was figs. 

Next question.  A stack of books is placed on a scale in an elevator. The scale reads 165 newtons.  The stack’s true weight is 165 newtons.  Can you tell if the elevator is moving at a constant velocity of 2 m/sec up, 2 m/sec down, or not moving?   Once I was able to stop thinking about bar cookies, I judged Youngest Daughter’s answer to be correct:  “Who would ever put a scale in an elevator?”  Clearly, this elevator is in the physics department at a major university.  My son told me later that no one in his physics class questioned the idea of placing a scale in an elevator.

We went on in this vein, until Youngest Daughter, who was trying to stand on her head on the couch, said to her brother, “I have a physics question for YOU.  If I fall off the couch at 3 meters per second, and I hit the ground in 13/10 of a second, how long is the ground away?”

Son:  “How LONG is the ground AWAY?  Three weeks?  In California?”

But he set to work, saying, “It’s more complicated than you think.  Because, unbeknownst to you, you are accelerating!” 

Youngest Daughter:  “I am?!”

After much calculating, he said, “This is a pretty big couch – it’s 4.381 meters high.”

Youngest Daughter:  “So, did I break my neck?”

Son:  “Probably.”

Then we moved on from Physics to English.  He showed me a 55 page single-spaced typed packet entitled “Concision” (meaning ‘leanness of words’).  ’Nuff said.

On to American History. 

Son:  “Who was the first man in space?”

Youngest Daughter:  “Louis Armstrong?”

Son:  “No!  There are two famous Armstrongs, and Louis Armstrong is one of them.”

Me:  “Lance Armstrong is the other.”

Son: “Well, there are three famous Armstrongs.”

Me:  “Yuri Gagarin.”

Son:  “Right.  Who was the first American in space?”

YD:  “Lance Armstrong?”

Son:  “Where was the Berlin Wall?”

Me:  “Who is buried in Grant’s tomb?”

Son:  “What are two civil rights laws passed during the Eisenhower years?”

YD:  “Thou shalt not shoot...”

Son:  “I don’t think there are any American laws that begin with ‘Thou shalt not.’”

I doubt this study session left my son any better prepared for his tests, but he did prove that I am NOT smarter than an 11th grader.