i saw this question on a practice ACT test. I ended up getting it wrong. it was something like: If you are sitting in row 6 of a train moving 150 mph and you flip a coin in the aisle what row will it land on? I picked the farthest one behind row 6. The answer is it will land in row 6. Can anyone please tell me how this happens?
Because the coin is moving at the same speed as the train and everything else in it. The speed of the coin relative to the train (zero) isn’t going to change, just because you toss it in the air. Next time you’re a passenger in a car on the highway, flip a coin. Does it smack you in the face at 55 miles per hour?
Well, when you’re sitting on the train, you and everything around you is moving forward with the train. This includes the coin. When you toss the coin up, it and you continue to move forward with the train. You’ve just goven the coin a little extra motion, upward. The coin rises and falls (continuing to move forward with you and the train), and lands back on you or your seat. Since you and the coin share the train’s forward motion, there is no relative motion between you and the train, and the motion of the coin looks like normal up-and-down motion as if you were sitting still.
Now, if you were to drop the coin off the back of the train, it, still sharing the train’s forward motion, would slam into the trackbed at a sideways velocity of 150 mph, plus whatever downward velocity it acquired after being dropped.
Also, if you’re sitting in row 6, you’re lucky, because you won’t have to walk as far to the exit at Waterloo International. Those Eurostar trains are long.
The coin, like the other contents of the car, is already moving forward 150 mph. Your flipping game isn’t going to affect its momentum appreciably; in real terms, it’s being propelled forward and upward simultaneously.
Now, if you were to flip the coin straight up while the train was at a dead stop and it lurched forward suddenly and with unbelievable speed while the coin was still in the air, it might wind up a few seats behind you. Your neck would probably snap, but it would be worth it knowing how you had advanced the cause of science.
Simply put in layman’s terms: The train, and all its contents, are moving at 150 mph. Thus, the tossed coin is moving with the train, as are all the air molecules on the train, etc., etc…
So, you observe the coin goes straight up over Row 6, and it comes straight down over Row 6. Since the coin is moving with the train, it will come straight down…hence, it is not flung several rows behind you. I’ll spare you the finer details about relative motion, etc… - Jinx
Can you imagine flipping a coin in a Boeing 757 if it that law of inertia did not apply? How about a piece of luggage falling from the overhead in the Concorde?
** stereonationpga** Welcome to the SDMB - I hope you aren’t taking the ACT any time soon.
It’s answered to death, but just wanted to point out that you can go bigger…when standing on the ground, why doesn’t the coin fly away at thousands of miles an hour due to the earth’s rotation?
(I tried to google the exact speed of that rotation and was surprised at how elusive the number is.)
It’s not terribly difficult to calculate. Googling reveals the Earth’s diameter to be 7,926 miles which gives a circumference of 24,900.3 miles. Knowing the Earth Rotates once approximately every 24 hours, we can divide the circumference by 24 and arrive at a rotational velocity of 1037.5 MPH.
One rotation per day, approximately.
At the equator, that’s about 24000 miles in 24 hours, or 1000 mph. Roughly, you multiply that times the cosine of your latitude to get your own speed (at the poles, where the cosine of 90 degrees is zero, there is no lateral speed due to rotation). Altitude, and the centrifictional bulge, would also factor in, but probably not as much as 24000 miles is off.
well it depends if the train is open to the air or not? if it is then the coin is going to go towards the back. Otherwise what they said.
How many open-air passenger trains that go 150mph have you been on?
On another message board that I visit, there’s a guy who claims that the Earth is completely stationary (and the Sun, moon and stars rotate about it), reasoning that “If you tried to walk East, the world would be coming at you at a thousand miles per hour” - he is completely resistant to reason (and in all honesty may actually be nothing more than a troll).
Of course, one must make the assumption that “flipping a coin” means tossing it straight up relative to the tosser. I know people who have trouble with that concept and have to run after a poorly tossed coin.
That figure is surprisingly close to the Monty Python lyrics -
“Just remember that we’re standing on a planet that’s evolving,
Revolving at nine hundred miles an hour…”
Apparently the lyrics were properly researched.
I always thought so, but I was never too sure. e.g. Is the planet really “orbiting it’s reckoned, at nineteen miles per second…” the sun ?
The parts of the lyrics that I’ve been able to check out have all been correct, so I’ll give this one the benefit of the doubt until someone drops contradictory information in my lap. Or in this thread. Either way, really.
Yep. Take the orbit to be circular with r=1.5x10^11 m and a year to be 365.25 days. You wind up with 28.9 km/s or 18.6 miles/sec.
Imagine the whiplash! 
From here: