A conceptual question ... imagine a car moving right to left as I look at it. The engine, gears, differential, and axle are applying a torque to the back wheels which rotate anti-clockwise as I look at it. If I look at the point of contact with the ground, the tyre is moving left to right, so there is a friction force acting right to left. This friction force is what is accelerating the car. If there was no friction, the tyre would spin with no forward force and just slip. So ... if I had a perfect frictionless drive train and no air resistance, friction would perpetually accelerate the car! Once you started a wheeled vehicle moving in sych conditions, how would it ever slow down? The only thing I can think of is that the normal force woukd act to slow the car since the tyre is not 100% rigid. Is my thinking wrong?!3 AnswersPhysics3 days ago
I saw a movie years ago I'm trying to remember the name of. It was about an architect, I think, and it was a sort of femme fatale film. His wife was psycho and eventually had this architect husband committed. When she came to the mental institution to gloat that she now had all his cash, he strangled her knowing that he could plead insanity!1 AnswerMovies3 months ago
The first is about algae blooms reducing the Earth's oxygen in the future, so scientists send a message back in time that's picked up by, I think, a scanning tunnelling microscope as noise that they decipher.
The second might be a short story and from what I recall, scientists were calculating out digits of PI and noticed them changing. They realised the calculation could affect the physical constants of the universe and some alien species was also tinkering with them.
Thanks!!3 AnswersBooks & Authors12 months ago
I live about 20km from an airport. Usually when jets pass, I hear the familiar rumble of their engines. Every now and then, presumably as they come in for landing, the sound suddenly appears as a long, hollow, meooooow sound that drops in pitch. I know it is probably the Doppler effect, but was wondering if landing gear or flaps being deployed are also responsible ...5 AnswersAircraft1 year ago
I'm referring to the global warming section. Level 7s ... can you move this back to that section if maliciously moved. Thanks!5 AnswersGlobal Warming1 year ago
I've noticed a strange phenomenon where as a full Moon rises, clouds suddenly stop moving and it goes eerily quiet. Yes, I'm aware the answer could be 'coincidence' but its something I've seen repeatedly. Just wondering if there is an actual reason for it ...3 AnswersGlobal Warming1 year ago
The reason I ask is there doesn't appear to be any new questions in ages!!5 AnswersGlobal Warming2 years ago
Suppose I have an equation something like a+b+c+d = 33, where a,b,c,d are positive integers between 1 and 10 ... how do I determine mathematically the number of solutions within those constraints? I know it must involve something like n!/(n-r!)r! ...
Also, how would I modify it to account for more or less additions (a+b+c+d+e+f, for example) or if the integers were 1-100 etc?
Thanks! Been driving me mental ...2 AnswersMathematics4 years ago
Let's suppose I have two tables X and Y. Both tables contain two elements so X = (5,3) and Y = (4,1).
Now suppose I don't know the values of the elements. But I do know the results of their addition. So I can write four equations representing the addition of each combination of table elements:
x1 + y1 = 9
x1 + y2 = 6
x2 + y1 = 7
x2 + y2 = 4
Am I right in thinking, actually, I can't work out the table elements based on these equations other than by making a 'logical guess' at the value of one of them?2 AnswersMathematics4 years ago
You have a starting point (Airport A) and finishing point (Airport B). If you fly between them, there's no guarantee that you'll end up on a path directly in front of the runway when you go to land.
So I can imagine you'd need three navigation points, Airport A, the end of the runway at Airport B, and Turn Point C which a point in line with the runway some distance out.
But here's the question - if you start turning the plane at C you'd have to compensate for the speed of the plane and the rate of turn otherwise you'd not line up. So how do pilots account for this?
Always wondered ... thanks!Aircraft4 years ago
After all, if the argument is that AGW is a leftist, liberal conspiracy, and scientists are manipulating the data, why wouldn't they change the data to remove the pause to avoid the problem in the first place?12 AnswersGlobal Warming6 years ago