The Magnus effect (often called the Magnus force and named after its 1852 discoverer Gustav Magnus) is a lift force of tremendous importance to all athletes who want to bend the flight of a ball.
Thomas recently informed me that by itself wind doesn't make any sound; what we hear is simply the wind hitting objects- our ears, for example. When wind blows against pine trees, you hear a particularly beautiful noise- some have likened it to a violin. I think it sounds very much like a mother soothing her baby.
Whatever the source, I am enjoying the sound of wind against pine from my pink bedroom which is now mercifully cool. As most of you know, Thomas installed something I believe is called "air conditioning" in the bedroom. (I do not ask, because then I will be culpable in a German court of law.) But the nights are much better now.
Our days our filled with the usual surf and chilly water and a ton of tennis on very hot courts. But there is also plenty of physics and math, alas. F signed up for a chunk of work and he is hacking away at it in high spirits. He plows through the math pretty much on his own, but with the physics he needs occasional help. Thomas doesn't skip a beat- (it would be like if someone asked me how many wives Henry the 8th had) he just turns slowly from looking at the British open (god help me during golf season) and says something that sounds like this:
"The derivative of the force times the speed of light minus the square of the sum of the Maxwell.
Don't forget, that q is a constant.".
Then Frederick nods and they go on. I must admit I am impressed at how Thomas' synapses still seem to be firing on all cylinders. (Did he not drink in college?) I know he didn't study...he just went to class. Just sat there got the gist of it and went to play tennis.
Gravity is what allows the game of tennis to be played. Without gravity, the ball wouldn't come down and bounce in the court after it was hit. A tennis ball is constantly undergoing an acceleration due to the force of gravity. The force of gravity acts downward on the ball, and is perpendicular to the court surface. An equation for the magnitude of the force of gravity on the ball is given by:
F_g=mg
Speaking of tennis, our teachers are one rather handsome former Portuguese champion and a really kind, not as young gentleman slated for hip surgery in a few weeks. It's insane. He is practically crippled, but whacks it back with nary a complain. On the contrary, he is crazy about Thomas- every thing Thomas does is praised and celebrated. I am not kidding-it's not entirely clear that he knows my name, and we play every day. The only thing he ever says in reaction to our shots is how wonderfully Thomas plays. I can be flaying around and he will offer nothing more than a detailed analysis of how squash has influenced Thomas' slice. Once he finally directed something at me- and all I heard was "very nice legs".
At which point I sort of rolled my eyes: fine whatever, look it you must, but hurry up about it.
It was only later that I realized he was talking about Thomas' legs....he was ruminating on how beautiful they were....how beautifully they covered the court. Or maybe he was talking about the looks of them (they aren't half bad), but in any case, he wasn't talking about mine.
I am going to send him the below photos of Thomas for his scrap book.
When a tennis racquet hits a tennis ball, the force of the racquet on the ball delivers an impulse to the ball while the ball is in contact with the racquet. The magnitude of the force of the racquet on the ball varies with time, starting low at initial contact, then reaching a maximum when the ball compression and racquet string deformity reaches a maximum, before reducing back to zero as the ball leaves the racquet strings. The Impulse-Momentum Theorem states that \vecJ=\vecp_f-\vecp_i=\Delta \vecp, where J is the impulse on the ball and p is the momentum of the ball.
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| pre dinner swim. |
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| Luis taking a break to attend to Thomas |
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| Physics in pink |
In what's left of our spare time, we have tried our hand at a few weighty questions, usually at restaurants. (The Wehlens love to rant in public.) For example:
Should we try to contact life in other planets even though it will take 50,000 years perhaps for a response, and the response might be hostile? Stephen Hawking, among others, thinks we should keep quiet.
Basically we came to the conclusion that it is better to be smarter and dead a little earlier, than dumb and dead anyway.
Or, why do hornets release a pheromone after they die that alerts the other hornets to attack? Is it to dissuade predators? and how does that work with natural selection? wouldn't the dying hornet's ability to release this die with him? (answer: the pheromone is released to protect the others by letting them know that danger is near. So the genetic advantage is not the releasing of the pheromone, but the ability to smell it.)
The Wehlens left yesterday, and then we got the very sad news about Jim H; so I for one am a little down. Thomas' mother has actually taught me a lot (without knowing it) about how to deal with the rough spots in life. Make tea; serve cake on fine china; work on your backhand volley. Nothing is meaningless. So for God's sake, keep the arms straight and the racket head up for a high ball to the backhand. That's all you can do.
But it's enough.
If a train is going through a tunnel that is half it's size, how close to the speed of light does the train have to be to become invisible to a person watching the tunnel... ?
Answer: I don't even know if the question is correct. Thomas is in charge of the physics homework.
PS Introducing a new Blog Segment called "GOOD NEWS FROM NASA" ....today's NYT:
'NASA Denies Trump’s Request to Send Astronauts Past the Moon on New Rocket'
(But keep the super ideas coming DT!!
