QUESTION:
I have a question about gravity So as we know gravity is significantly less on high mountains or tall buildings and increases as we lose height. My question is that if we have 2 objects with the same volume and mass, 1 falls on a mountain and one falls on a beach ( note that they are released from the same height based on the surface they shall fall on ) Will they both reach the ground at the same time or will their speeds be different?
ANSWER:
If you neglect air drag, the one on the mountain will experience a smaller weight force and will therefore have a smaller acceleration. It will therefore arrive at the ground later and with a smaller velocity. But air drag might very well not be negligible. On the mountain top the air density is less dense than at sea level and therefore the air drag will be smaller. Now it is a more ccomplicated problem. If, in addition to your stipulation of equal masses and volumes we stipulate the same shapes, the time it would take to reach the bottom would depend on the height of the mountain and the height of the fall. (I have assumed that the height of the fall is small enough that one can approximate that the change of air density and the gravitational force are negligible.)
QUESTION:
If a fly was the bottom of the cylinder that weights 100 n. And then the fly flies around the open cylinder what is the weight of the clyinder is less than 100 or equal to 100n
ANSWER:
Also important is the weight of the air in the cylinder. The weight of the cylinder is always equal to 100 N; the question is: if the cylinder (and fly at rest) are sitting on a scale, what does the scale read when the fly flies? See an earlier answer.
QUESTION:
Does light itself have heat? My college roommate and I got into this debate but he seems to think his physics book says light has heat but most of the sources I read say that only the absorption of light causes heat.
ANSWER:
This question has no answer because heat is defined as the flow of energy, not an amount of energy. For a detailed discussion of thermodynamic terminolgy, see an earlier answer.
QUESTION:
It seems evident that global warming is driving more moisture into the atmosphere. Is it possible that moisture is escaping to low-earth orbit, never to return?
ANSWER:
The velocity necessary to achieve near-earth orbit is about 18,000 mph. The most probable speed of a water molecule at 120°F is about 1220 mph. Escape velocity from the earth is about 25,000 mph. I don't think you need to worry too much about water molecules escaping from earth.
QUESTION:
I've seen that a recent AI analysis of particle collider data suggests that a proton has an extra charm and anti charm quirks, if this analysis proves to be a discovery above sigma 5, could it help explain dark matter? I just haven't seen anyone talk about this, thanks in advance
ANSWER:
Why would you think this would have anything to do with dark matter? The mass of the proton is known to high accuracy so these data would only alter the model for the internal structure of a proton, not its mass. No change in mass means no solution to the unknown extra mass supposedly implying dark matter.
QUESTION:
let's say a bag of rice was dumped from a flying plane, and you knew every conditions that would act on each grain. Every gust of wind, complete topographical information, the position of each grain of rice, exact gravity force, everything. If you had unlimited resources, computing power, time etc. Would it be able to calculate where every grain of rice would end up?
ANSWER:
These are some pretty severe suppositions you are placing. And you did not include effects on the grains due to their shapes. Let's start with a single grain. In principle this is a classical mechanics problem, solvable. But there are some serious problems with what will surely be a major contributor to the problem, air drag; there are quite good approximations for the air drag force, but they are not exact. For that reason, you could only predict approximately where any particular grain would land. If there are many grains, there will be interactions among them. These interactions would be mainly due to disruptions in the air flow due to the motion of the grains themselves; and if two grains collide, it would be virtually impossible to predict the velocity of each after the collision. Maybe most important is that the motion of the air is chaotic, not predictable for any particular position at any predictable time. I could envision the positions being predictable if the experiment were performed in a perfect vacuum and care was taken in dumping them that they be far enough apart that they never suffer a collision.
QUESTION:
If I were in London England and launched a drone with 6 hours of battery and set it to hoover perfectly still, when the battery died would the drone land in London or America?
ANSWER:
What you need to understand is that your drone is rotating around the earth's axis just like anything "at rest" is. When you set it up to hover over London it is already moving right along with London. The drone flies relative to the air, so if you set it up when the air is still and if later a wind starts blowing, the drone will move with the wind; but it will certainly not get blown as far as America is from London in six hours.
QUESTION:
We're having a lively debate at work regarding best driving practices for fuel economy, ad we've finally settled into two camps on one specific topic; what to do when approaching a hill. Group 1 believes that the driver should always coast on downslopes and never touch the gas. Their reasoning being to cash in on all the free momentum you can get. The 2nd group of us dissent and claim that's exactly when you should accelerate, with the rationale of using gravity as a catalyst for a more fuel efficient fuel burn. Is there a clear cut answer to this; and if not, what's a good way to think about the problem?
ANSWER:
As you go down the hill do you suppose you use more fuel when coasting or accelerating? It seems to me the answer is obvious. Suppose the hill is 1 mile long and the accelerating car consumes 0.1 gallons of gas and the coasting car consumes 0.05 gallons; for that leg of your trip the coasting has 20 mpg and the accelerating has 10 mpg. If your car is a hybrid you will consume no gas and the energy you gain by speeding up will be saved in the batteries so this mile was free when computing mpg. I'm afraid that "using gravity as a catalyst for a more fuel efficient fuel burn" means nothing to me.
QUESTION:
When radiation passes through a GM-tube the gas inside is ionised. How come that a GM-tube is reusable if the atoms in the gas change. They lose electrons, so those atoms wouldn't be able to absorb the energy of the radiation the same as gas that hasn't already been ionised. So wouldn't the gas that can be ionised eventually run out?
ANSWER:
These tubes are filled with a noble gas, helium, neon, argon, etc. Many atoms (let's say N) become ionized as the radiation passes through the gas. But they don't stay ionized because the we now have N free electrons and N positive ions and they recombine because the Coulomb force attracts electrons to to the ions.
QUESTION:
I am out of high school and looking to strengthen my understanding of physics, this question has been bugging me. For third law, it states that every action force has an equal or opposite reaction. How does third law apply to rockets? Everyone tells me that it is the act of throwing something or the opposite reaction force that propels the rocket or the balloon, but I think they are all wrong it is not because of the releasing of the fluid, I think it is the net force within the system of the rocket ship or the balloon that pushes it up. Am I correct?
ANSWER:
I suggest that you read a recent answer on jet ski propulsion. This addresses the issues about rocket propulsion. Your explanation for rocket propulsion is wrong. Newton's third law is indeed the correct explanation.
FOLLOWUP QUESTION:
So I read the dialogue/conversation(chat?) about the seadoo and the "friend" and yes you are completely right (obviously) about how the seadoo would still acccelerate even on air, it's just a different medium. The breakdown of the engine makes complete sense to me aswell, and 100% third law applies, from the impeller being attached to the boat or the body of the vessel and the impeler is forcing out water to the nozzel, so impeller pushe water out water has interaction with impeller impeller is pushed by water in opposite direction voila movement. But from the little information I gathered, it seems rocket engines are different. They are like mini explosions that are contained, and I understand third law is still applied when in earth atmosphere and stratosphere the air will cause drag from it interacting with the vessel but third law doesn't make sense in space which has no air ( their are particles in space like neutrinos traveling understandablly but rockets don't push off of that light sails do.) the point is with the seadoo it is interacting with the water medium and in the other example the air medium to traverse. But in space I think third law does not apply, due to their being a vacuum. But yeah on earth it makes sense, the thrust has to overcome the force air has on the rocket or the drag, so Newtons third applies to earth but I don't think for space.
ANSWER:
A jet engine draws air from the atmosphere and adds kinetic energy (speeds it up using a fan driven by fuel carried in the airplane) to the air which it ejects out the back; the reason that this will not work in space is that there is no air to draw in, NOT because the jet needs air to "push against". The same principle applies to the jet ski motor but water is the propellant, not air; the air has nothing to do with why the jet ski works outside of the water (be sure to note that the question of the 'friend' states "…with a source of incoming water for the water pump inside it…"). It would work just as well in space as long as you fed it water; similarly, a jet engine would work just fine in space as long as you provided it with air. A rocket engine works on exactly the same principle as a jet engine except that the fuel itself is both the impeller and the impelled. Something gives kinetic energy to the molecules (your little explosions); that something is chemistry. But each molecule which is going faster than it originally was, has experienced a force accelerating it out the nozzle and therefore the exiting molecule exerts an equal force back on the rocket ship.
Alas, I believe that one of the most used and least understood principles in physics is action/reaction to describe Newton's third law. Those words should be discarded and the statement of the law should be "If object A exerts a force on object B, object B exerts an equal and opposite force on object A".
