• ### Why is Mastering Physics So hard?

8 answers · 20 hours ago
• ### According to physics, do past and future exist?

18 answers · 6 days ago
• ### If there were a space ship in space, and a propeller engine thrusting air against the front of the ship, would it accelerate? more details?

So say you have a space craft sitting in space. It rotates for artificial gravity and there is a mag lev track for a mag lev sled to hover on. Now say the mag lev sled has a propeller engine on it. The sled thrusts air against the front of the ship while thrusting itself backwards. Now lets pretend the propeller... show more
So say you have a space craft sitting in space. It rotates for artificial gravity and there is a mag lev track for a mag lev sled to hover on. Now say the mag lev sled has a propeller engine on it. The sled thrusts air against the front of the ship while thrusting itself backwards. Now lets pretend the propeller engine which is driving the ship forward somehow never runs out of the mag lev track that it's sitting on. It continues thrusting air forward to drive the ship but does not run out of track. I know it sounds silly but humor me....
10 answers · 3 days ago
• ### You drop a rock down a very deep well. you hear the splash after 9 seconds. how deep is the well?

6 answers · 22 hours ago
• ### How to Calculate the force of gravity at 200 km above the Earth s surface?

6 answers · 1 day ago
• ### Can acceleration change in an accelerated rate?

Best answer: Of course. Before people use the term "jerk" to describe it, I used the term "shock". The rate of change of acceleration is extremely important in many situations. For example on a railway if the train suddenly enters a curve the people on board experience a sudden force and fall over. So a... show more
Best answer: Of course. Before people use the term "jerk" to describe it, I used the term "shock". The rate of change of acceleration is extremely important in many situations.

For example on a railway if the train suddenly enters a curve the people on board experience a sudden force and fall over.
So a transition curve was introduced 170 years ago. Where the radius of curvature progressively increased from infinite until it reached the correct radius. So that the force increased linearly from zero.

Today we realize that the fourth power is even important.
So that the rate of change of the force is not linear. It increases slowly at first then the rate of increase gradually increases. Humans can predict this better so they go around a corner faster with less discomfort.

ie we are specifying a = k t^2

Other situations. You can apply a force to a piece of glass and it doesn't break. But if you increase the force SUDDENLY (a high shock or jerk) then only the part of the glass near the point of contact is accelerated initially.
The rest is still stationary. The stresses cause the glass to shatter.

So the shock ( or jerk) breaks the glass.
We call such materials "brittle" in that they cannot withstand a high RATE OF CHANGE of acceleration.

In effect we knew this thousands of years before physics was invented.
6 answers · 1 day ago
• ### What is the difference between thrust and velocity? I failed high school physics, so please don't just give me a formula.?

5 answers · 15 hours ago
• ### Is ball-lightning for real or a myth?

how can scientists prove it's real or not?
how can scientists prove it's real or not?
6 answers · 2 days ago
• ### If the earth moves in curved space time, why do lasers make a perfectly straight line?

15 answers · 1 week ago
• ### Given your understanding of physics, is time travel (as we see it depicted in movies and in novels) possible? Could we do this one day?

Its true that we have never encountered time travelers from the future or the past that are in any way verifiable. Do you think time travel is possible? Will we ever do it? I say NO. Its not possible as the future simply never exists until it happens, and then its not the future. As for traveling to the past. ... show more
Its true that we have never encountered time travelers from the future or the past that are in any way verifiable. Do you think time travel is possible? Will we ever do it? I say NO. Its not possible as the future simply never exists until it happens, and then its not the future. As for traveling to the past. Same kind of answer. It would no longer be the past if we went there, it would be something else.
6 answers · 2 days ago
• ### A car is traveling at 58.2 km/h on a flat highway?

m/2*V^2/3.6^2 = m*g*μw*d
mass m cross
d = 58.2^2/(3.6^2*9.81*0.155) = 85.94 m

m/2*V^2/3.6^2 = m*g*μd*d
mass m cross
d = 58.2^2/(3.6^2*9.81*0.518) = 25.72 m
m/2*V^2/3.6^2 = m*g*μw*d
mass m cross
d = 58.2^2/(3.6^2*9.81*0.155) = 85.94 m

m/2*V^2/3.6^2 = m*g*μd*d
mass m cross
d = 58.2^2/(3.6^2*9.81*0.518) = 25.72 m
4 answers · 2 days ago
• ### Is visible light more special than other spectrums of electromagnetic radiation(except for being able to be seen by human eyes)?

12 answers · 6 days ago
• ### What is the most difficult branch of physics?

8 answers · 4 days ago
• ### What is the meaning of this symbol a sideways B from a newspaper article from 1874?

5 answers · 3 days ago
• ### Bouncing batteries. I'm trying to figure out why a discharged AA alkaline battery will bounce when dropped on end and one with a full char..?

4 answers · 2 days ago
• ### How real is time travel?

21 answers · 1 week ago
• ### Are radio waves, infrared, visible light, ultraviolet, x-ray, gamma ray really the very similar things thag have different wavelengths and?

frequencies
frequencies
5 answers · 4 days ago
• ### Why is it that when something spins really fast, at some point it almost seems as if it's begun going backwards?

Best answer: I believe that you were doing this indoors with a light on. Unlike sunlight the power produces light which fluctuates. If the power is 50 hz then you see 100 bright flashes of light each second ( with a corresponding 100 dark periods ). Ok so when the spinner is going slowly lets say 1 turn per second then you... show more
Best answer: I believe that you were doing this indoors with a light on.
Unlike sunlight the power produces light which fluctuates.
If the power is 50 hz then you see 100 bright flashes of light each second ( with a corresponding 100 dark periods ).

Ok so when the spinner is going slowly lets say 1 turn per second then you actually see 100 different images of it 3.6 degrees apart. If there are 3 legs on your spinner this represents about 1/33 of the distance to the next arm.
So you see it going forwards.

Now you increase the speed to 15 turns in one second.
between each flash the spinner turns 15/100 of a turn or about 54 degrees. This is just less than half way to the next spinner arm.

But if you increase the speed further to 20 turns per second then the spinner has moved forwards by 72 degrees.

Now your brain steps in. Has it moved forwards by 72 degrees or backwards by 48 degrees.
It isn't possible to tell the difference so you brain automatically concludes the simpler of the two answers.
ie it has started to turn backwards. And speeding it up further makes its backwards turn slower until at a speed of 33 turns per second it would appear stationary.
4 answers · 3 days ago
• ### What causes the magnetic poles of the earth to reverse?

Best answer: The magnetic field is produced by the rotation of the iron core, which as a ferrous material loves to give and receive magnetism. One theory is that the liquid part of the iron is subject to occasional swirling, which changes the alignment of the magnetic material.
Best answer: The magnetic field is produced by the rotation of the iron core, which as a ferrous material loves to give and receive magnetism. One theory is that the liquid part of the iron is subject to occasional swirling, which changes the alignment of the magnetic material.
4 answers · 3 days ago
• ### How many frames per second is real life?

Best answer: With some careful setups, human eye can tell the difference between 100 frames per second and "continuous". For sounds, most people can tell the difference between 1000 Hz and 1016 Hz, even when the sounds are separated by several seconds. So overall, I would say that for humans, real life is at least 125... show more
Best answer: With some careful setups, human eye can tell the difference between 100 frames per second and "continuous". For sounds, most people can tell the difference between 1000 Hz and 1016 Hz, even when the sounds are separated by several seconds. So overall, I would say that for humans, real life is at least 125 frames per second.
4 answers · 3 days ago