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11/3/2022 9:41pm
OK guys, I've been thinking of starting a physics thread, because I love the subject and I'm somewhat knowledgeable in the basics. However, even though I've had a few college courses, I'm no expert. Therefore, I'd love it if you guys who know more than I do can help out in this thread. Please post up!
My first entry will be to criticize a movie I saw once: Speed 2. Their first mistake was not to get Keanu back for the sequel; the second was to make that steaming pile of drivel in the first place.
The third is a gigantic error in their understanding of physics. In the movie, a cruise ship is hijacked, and the bridge is locked with the steering pointing at a port of call. The engines are all-ahead full, and the massive ship plows into the beach, then continues up the surface of the land for quite some time. All this is plausible, and in fact something with that much mass would, in fact, continue moving for a long time.
Where the mistake is made was obviously for effect, but it actually makes me angry: the main character is standing in some anteroom when the impact with the beach occurs. The director used all kinds of multiple-angle shots of the guy flailing through the air, crashing through windows, rolling across the deck, crashing through more windows and doors, then finally coming to rest after grabbing onto a handrail at the very front of the ship. Apparently, they wanted to illustrate how much mass and power are brought to bear when a ship runs aground.
There are two problems here: One, the standing man's inertia would only carry him with whatever velocity he carried in his mass alone when the ship stops; not some massive, unstoppable force. Two, since the ship is so massive and takes a long time to slow down, the difference between all-ahead full and all-ahead full with the hull scraping on the ground would be small. In fact, a man standing on the deck of such a ship would feel a jolt but might not even lose his balance.
The movie misunderstands there is a big difference between inertia, a body's tendency to remain in motion, and velocity, which is speed in a specific direction.
Let's hear some more movie mistakes, cool tidbits, unique experiences, and other physics fun facts.
My first entry will be to criticize a movie I saw once: Speed 2. Their first mistake was not to get Keanu back for the sequel; the second was to make that steaming pile of drivel in the first place.
The third is a gigantic error in their understanding of physics. In the movie, a cruise ship is hijacked, and the bridge is locked with the steering pointing at a port of call. The engines are all-ahead full, and the massive ship plows into the beach, then continues up the surface of the land for quite some time. All this is plausible, and in fact something with that much mass would, in fact, continue moving for a long time.
Where the mistake is made was obviously for effect, but it actually makes me angry: the main character is standing in some anteroom when the impact with the beach occurs. The director used all kinds of multiple-angle shots of the guy flailing through the air, crashing through windows, rolling across the deck, crashing through more windows and doors, then finally coming to rest after grabbing onto a handrail at the very front of the ship. Apparently, they wanted to illustrate how much mass and power are brought to bear when a ship runs aground.
There are two problems here: One, the standing man's inertia would only carry him with whatever velocity he carried in his mass alone when the ship stops; not some massive, unstoppable force. Two, since the ship is so massive and takes a long time to slow down, the difference between all-ahead full and all-ahead full with the hull scraping on the ground would be small. In fact, a man standing on the deck of such a ship would feel a jolt but might not even lose his balance.
The movie misunderstands there is a big difference between inertia, a body's tendency to remain in motion, and velocity, which is speed in a specific direction.
Let's hear some more movie mistakes, cool tidbits, unique experiences, and other physics fun facts.
edit: is hydrodynamics apart of physics?
Weed and hores next door😬
I thought this was cool... but then again, im an idiot.
The Shop
Sophomore year he has a student teacher come in for biology/chem1 and that moron could only read out of a tect book. Was horrible ... didn't matter as we moved a month into the school year.
Teachers can make a difference.
Theory being that at the equator you have centrifugal force acting against the earth’s gravity, but the same can’t be said for at the poles…
And if you did weigh more at the poles, how would you know? The bathroom scales would be affected by the same amount…
Oh, and it makes your point.
I'm jus' sayin'...
In that order. Romaniacs indeed.
I didn't think to mention before that the slight bulge at the equator lessens your body weight also, since you are slightly farther away from the center of the Earth.
And if there was a hole straight through the earth and you jumped down it, you would cycle back and forth (you’d be going ‘up’ once you passed the centre and so would reverse direction).
Pit Row
A bullet, upon leaving the muzzle of a gun, drops to the ground as quickly as if you had dropped it from your hand.
The bullet starts dropping immediately.
I've had this argument so many times.
People think that since many larger caliber rounds can be zero at 25 and 100 yards but high at 50, the bullet "must" be going up at 25, and somewhere around 50 starts back down .
It's just "line of sight". Bullets can't do that.
Typically a heavier bullet for a given caliber will require more twist to stabilize it, not necessarily because of the weight but because of the length. See you cant make the bullet and bigger around so the heavier ones are longer to gain the extra weight. Of course there are some exceptions due to actual bullet construction/materials.
Which leads into a 1:10 twist being faster than a 1:12 twist which seems backwards untill you think about it.
Also in long range load development, "watching" the barrel move in and out of its harmonic "sweet spot" as you make the loads hotter and hotter is pretty cool. Reading about it is one thing, but seeing it in person is truely fascinating to watch.
Remind me again how a boat tail works. Haha
If it were fired upward, the bullet would travel upward until it meets the highest point, then descend. If fired downward, it is already on the descent. Note that if the barrel were to be located on the ground, yet firing upward (imagine the rest of the gun is buried,) the ascent and descent would take the same amount of time.
All the above is excepting a small amount of atmospheric friction, of course.
My friend still thinks that bullets go in a perfectly straight line for some amount of time after leaving the barrel, while gravity is suspended because of the sheer velocity of the bullet. I can't get him to agree that gravity never takes a vacation, no matter how fast something is traveling. (At least in Newtonian physics.)
https://www.wired.com/2009/10/mythbusters-bringing-on-the-physics-bulle…
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