Wikipedia:Reference desk/Archives/Science/2018 November 22

= November 22 =

What's the scientific explanation for the damage of over-watering fruits trees?
I read that it's dangerous for trees to be too much watered. What's the scientific explanation for the damage of over-watering fruits trees? In addition, I've never saw fruits trees growth in water like lakes or any kind of accumulation of water. What's the scientific reason for that? --93.126.116.89 (talk) 05:02, 22 November 2018 (UTC)


 * https://www.scienceabc.com/nature/why-does-over-watering-kill-plants.html


 * http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/environmental/overwatering.aspx

Basically the plant roots die and rot for the exact same reasons you would die and rot if I submerged you under water for a long enough time. --Guy Macon (talk) 06:06, 22 November 2018 (UTC)
 * Waterlogging (agriculture) touches upon this question; in essence, that for most plants, the roots need access to air as well as water. Klbrain (talk) 01:16, 23 November 2018 (UTC)
 * A little more technical detail at Fact Sheets: Water-Logging from a consortium of Australian universities and government agencies.
 * If plant leaves breathe in CO2 and output O2 was waste, and plant roots breathe in O2, then what does that output for waste? Thanks. 67.175.224.138 (talk) 21:08, 30 November 2018 (UTC).


 * In addition to the problem of root rot and root death, caused by water saturation within the growing medium, plants that bear commercially important fruit can also suffer from their fruits splitting due to an uneven water supply, particularly when wet conditions follow a dry spell ("Splitting ... is most usually brought about when rapid growth is induced by the onset of wet conditions following a long dry spell. Related symptoms include the development of hollow fruit on apples" (Pests, Diseases and Disorders of Garden Plants by Buckzacki S. and Harris K., Collins, 1998, p605). PaleCloudedWhite (talk) 15:02, 28 November 2018 (UTC)

Underside of car scraping on ramps
When I drive my car down a ramp, say at a car park, I've noticed that if I go a tiny bit too quickly ("quickly" being relative - I'm still going very very slowly), the underside can scrape on the ground when I level out. But if I go slowly, there's no scraping. But surely the car is following the same path, regardless of speed? What is it that's causing my (bog standard hatchback) to be lower when I drive at, say, 6 mph, than when I drive at, say, 3mph? --Dweller (talk) Become old fashioned! 09:56, 22 November 2018 (UTC)
 * The vertical momentum of the weight of the car at 6mph is twice that at 3mph, so it causes the car's suspension to go significantly lower. The effect is more noticeable in cars with "soft" suspension.   Dbfirs  10:03, 22 November 2018 (UTC)
 * So when I drive at 60mph (on the flat, I hasten to add), the car is 20 times lower than at 3mph? --Dweller (talk) Become old fashioned! 10:33, 22 November 2018 (UTC)
 * No. Your question relates to driving down a ramp and then transitioning to a horizontal surface. As the car transitions to horizontal motion, its vertical momentum is eliminated by the impulse of an additional upward force that causes the car's suspension to compress more than usual. The response from Dbfirs is entirely correct. (When you are driving on the flat, you aren't driving down a ramp, are you?) Dolphin ( t ) 10:45, 22 November 2018 (UTC)
 * (ec) No. On the flat your vertical momentum is zero whatever speed you drive. I suggest you check under the front spoiler which may be scratched. DroneB (talk) 10:48, 22 November 2018 (UTC)
 * Even on a flat road analysing the behavior of cars over speedhumps is quite complex. The dampers provide a vertical velocity dependent, non linear force, and your jounce bumpers provide a non linear displacement related force. Your tires aren't especially linear, and you have the added complexity of a 2D contact problem. The mass of the tire locally at the contact point is a significant contributor. I model this stuff in my day job, I'm not convinced that there are any general rules of thumb. I would point out that some cars seem to be very tolerant of high speeds over speedhumps, others are not. Greglocock (talk) 10:58, 22 November 2018 (UTC)

Thanks for the replies, guys. Would inflating my tyres more potentially assist with this? (Yes, I know I can drive slower!) --Dweller (talk) Become old fashioned! 11:17, 22 November 2018 (UTC)
 * The extra fraction of an inch gained by over-inflating the tyres might have a very slight effect, but the answer is really just to drive more slowly. I once had a car with added suspension springs that helped prevent "bottoming out", but I don't know whether these can be fitted to modern vehicles.   D<i style="color: #0cf;">b</i><i style="color: #4fc;">f</i><i style="color: #6f6;">i</i><i style="color: #4e4;">r</i><i style="color: #4a4">s</i>  11:29, 22 November 2018 (UTC)
 * Thanks. --Dweller (talk) Become old fashioned! 12:06, 22 November 2018 (UTC)


 * Pumping up your tires will improve your fuel economy but will also seriously mess up the road holding of your car. I assume you drive a normal car so consequently the ramp is not constructed correctly. --Kharon (talk) 22:51, 22 November 2018 (UTC)
 * And it's dangerous, due to both said handling issues as well as the possibility of damaging the tire and causing a blowout. Unless you're a professional racing/stunt/etc. driver, inflate the tires to the manufacturer's specifications. --47.146.63.87 (talk) 07:38, 23 November 2018 (UTC)
 * Approaching the bottom of the ramp at an angle will help.--Shantavira|feed me 11:59, 23 November 2018 (UTC)
 * I don't think "Approaching the bottom of the ramp at an angle will help". The suspension springs on one side of the car would receive the Impulse (physics) that would otherwise be distributed to suspension springs on both sides of the car. This might actually exacerbate the problem. Bus stop (talk) 03:39, 28 November 2018 (UTC)
 * It does help. If you can do it arbitrarily slow, you can make the impulse exerted in springs arbitrarily weak (and you should absolutely do this, even at 10 km/h you can knock things loose in the engine bay if you keep hitting it), and the car's tilting movement will occur more along the left-right axis where the crest or the trough needs to have a much smaller radius to cause scraping/bottoming out. I have this issue when exiting my garage, which is on the top of a steep incline: backing out straight causes me to scrape the bottom of the door frame, but backing out while turning avoids it. 93.138.40.118 (talk) 06:28, 28 November 2018 (UTC)
 * "If you can do it arbitrarily slow", of course the problem goes away. I think this question is comparable to questions involving speed bumps. Is it advantageous to approach speed bumps at an angle as opposed to straight on? Bus stop (talk) 13:51, 28 November 2018 (UTC)
 * Or hire yourself a Bulldozer and pay back all the brutal scratching to that mean ramp! --Kharon (talk) 00:30, 26 November 2018 (UTC)

Sex/gender in tennis
I'm aware that tennis is a sport where professional female competition is taken seriously, though I know little about tennis. I've asked more than one tennis fan if top female tennis players would stand a chance against top male players, and the answer has been a resounding "no".

Presumably this has to do with sex differences, but what? I know men are generally stronger, but the Williams sisters look fairly strong to me, perhaps stronger than e.g. Tim Henman. So what attributes do men have over women pertaining to tennis? — Preceding unsigned comment added by Star trooper man (talk • contribs) 12:43, 22 November 2018 (UTC)
 * See Battle of the Sexes (tennis), which doesn't give a definitive answer but is an interesting read. Here's a good article on the topic. I liked this comment: "as a matter of public discourse, the premise should be rejected and the answer should have been: “who cares?” The best woman would not likely beat the best male or the 100th male or even the 500th male. The same way Alabama would not beat the worst NFL team. Different leagues, different classes of competition, different bodies. Yet millions of fans are entertained watching Alabama and prefer college football to the NFL. Why? All sorts of reasons, some tribal, some aesthetic. But mostly because, against their relevant competition, Alabama is the best. The end. Likewise, Serena Williams competes in women’s tennis and is the best there ever was. End of discussion. She would not beat Nadal. She would also lose a race to Usain Bolt, a fight to Ronda Rousey, and regatta in the America’s Cup. And so what?" --Dweller (talk) Become old fashioned! 12:58, 22 November 2018 (UTC)
 * Answering the main aspect of your question, I've heard it mentioned (not got time now for RS) that men hit the ball a lot harder on average, meaning faster serves, harder ground strokes. There's probably a stamina difference, as notoriously for this issue, men are required to play 5 sets in many tournaments, and women are not. We also see from athletics, that male athletes are a lot faster runners, and higher jumpers. Men are also on average taller, which helps. --Dweller (talk) Become old fashioned! 13:01, 22 November 2018 (UTC)


 * There are other relevant factors here to take into account. Earnings of tennis players outside of the top 20 are not so good, the further down the list you go the more of a struggle it is to exercise hard enough, pay the bills for travel and staying in not too bad accommodations. So, even if Serena Williams were as good as the nr. 50 of the men's game, it's not a fair comparison between her and that nr. 50 on the men's list who cannot afford the best trainers money can buy for him.


 * This is then also a problem for letting women participate in the men's competition. If Williams is allowed to boost her income by playing matches in the men's game, then some of the men who fall a bit short of being able to make it into the top 20 could reasonably argue that they should be allowed to play against women in the women's competition. They would have a good chance of winning tournaments there, greatly boosting their income. So, what would end up happening is that the women's competition would end up becoming a second-league competition formally for both men and women, but women would end up being pushed down the list. There would be no great female tennis players anymore as the future Williams would not earn enough to afford good training facilities to develop her talent. Count Iblis (talk) 16:34, 22 November 2018 (UTC)


 * You might be interested in the views of Renée Richards, one of the first transgender athletes who took her case to court (no pun intended):
 * Richards has since expressed ambivalence about her legacy, and came to believe her past as a man provided her with advantages over her competitors, saying "Having lived for the past 30 years, I know if I'd had surgery at the age of 22, and then at 24 went on the tour, no genetic woman in the world would have been able to come close to me. And so I've reconsidered my opinion."
 * --Carbon Caryatid (talk) 21:09, 30 November 2018 (UTC)