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-2
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0answers
41 views

Satellite collides with earth [duplicate]

Suppose we have a satellite in a circular orbit around the earth. We know that the velocity is given by $$v = \sqrt{\frac{GM}{r}}$$ I'm curious as to what conditions on a velocity change would require ...
0
votes
1answer
47 views

How much extra CO2 is produced (in the EU) each year due to the introduction of manatory car headlights during daylight hours? [closed]

Forcing drivers to keep their lights on during daylight hours may increase road safety, but there must be an environmental impact (not to mention a financial benefit to certain organisations). I am ...
-1
votes
0answers
43 views

How fast was the car going that hit me? [closed]

Can someone help? We were in a car wreck and I'm trying to figure out how fast the lady who hit us was going. She told the police 50 mph, but I don't believe it. We were going through an intersection ...
1
vote
1answer
43 views

Change in gravitational effect between Earth and the Sun

SPOILERS FOR "INDEPENDENCE DAY: RESURGENCE" ABOUND. I just watch ID:R and had a question about a plot point. In the movie, a large alien ship, which looked to be about 10-20 percent the size of Earth ...
0
votes
1answer
59 views

How noticeable is the gravitational pull of a mountain range?

A massive object like a planet exerts a great gravitational pull on nearby objects. This will cause them to accelerate towards the center of the planet with the same acceleration regardless of their ...
4
votes
1answer
279 views

Why do planets not radiate EM waves in their orbits?

Despite being overall near-netural, I would expect the individual electrons and proton to radiate long EM waves as we accelerate around the Sun or rotate around our poles. Is the acceleration so small ...
-1
votes
0answers
21 views

Is there anyway formula to calculate the heat produced by the burning glass and lenses?

Am just doing a simple project with burning glass. Is there any formula to find heat produced by it relating with the focal length or magnification of lens as well as mirror too?
5
votes
2answers
63 views

How much mass must Earth lose to lose its Moon?

Maybe I am wrong about the basic concept here, but for my curiosity: how much mass would need to leave the Earth (like satellites and rockets) to create an imbalance between the Earth and Moon so that ...
-3
votes
1answer
46 views

Who will feel more pain when jumping from a height, a tall man or a short man? [closed]

Whether the impact on a tall man is greater than a short man when he jumps from a height?
3
votes
2answers
69 views

What is the time required for water at 10 deg C to reach room temperature?

I have a small container (100mm X 80mm X 60mm) filled with water at 10° C. The container is made out of Aluminum and is not insulated, and is resting on a wooden table. Room temperature is about 27° C....
1
vote
1answer
64 views

By how much does the temperature of a cool Cola can increase by condensation of the ambient moisture on its surface?

Assuming standard ambient temperature and pressure, how can we estimate the increase in the temperature of a typical, cool beverage can produced by the condensation of ambient moisture on its surface? ...
4
votes
2answers
144 views

Weight Distribution of granular piles

I was recently at a farm watching piles of grain being formed in the shape of enormous cones. Each of these grain stacks weighs in excess of 50 tonnes. I am not a physicist but I am very curious as to ...
0
votes
2answers
84 views

If I throw or kick a ball, how much will the Earth move in the opposite direction?

I understand that for momentum to be conserved, if I throw a tennis ball (or kick a football) the Earth must move in the opposite direction to the ball. Obviously this is an infinitesimally small ...
0
votes
1answer
33 views

How to estimate a drag of flow reversing cylinder?

I am assuming a turbulent flow and a full reversal of the flow (in the picture the arrows are at non-straight angle but please consider the skew as negligible). Assuming we are talking about regular ...
0
votes
1answer
46 views

Effect of a nuclear weapon on the Moon

In some science fiction novel, there is the scenario of using nuclear weapons to deflect an Earth-approaching asteroid. But the question is, is a nuclear weapon really as useful on the moon or an ...
18
votes
2answers
1k views

How far can we separate two bound quarks?

If we try to separate two quarks bound into a meson or a hadron, the energy in the gluon field eventually will be large enough to spawn a quark-antiquark pair. How far can we stretch that gluon ...
60
votes
1answer
8k views

If we had a “perfectly efficient” computer and all the energy in the Milky-way available, what number could it count to?

The idea for this question comes from an example in cryptography, where supposedly 256-bit symmetric keys will be enough for all time to come (brute-forcing a 256-bit key is sort-of equivalent to ...
2
votes
1answer
47 views

How can you find the impact necessary to change the direction of Earth's spin?

If an object the mass of the moon was to hit earth's surface at an angle that would be in the opposite direction of earth's spin, how can you find how much momentum the object needs to cause earth to ...
4
votes
3answers
199 views

If an astronaut had stationed in International Space Station for the duration of mission, 17 years, would he be older?

Today the NASA International Space Station started the 100000 orbit after 17 years in the space. I just wonder if there were a team of astronauts which were in the Lab for all the duration of last 17 ...
11
votes
1answer
2k views

How much energy can be extracted by lowering something into a black hole? [duplicate]

If an object is in orbit around a star, the object has gravitational potential energy that could possibly be extracted. For example, when we perform gravitational slingshots around Jupiter, our ...
0
votes
1answer
87 views

What is the best way to calculate impact time with collisions?

I've been teaching myself physics and I've been wondering about the impact time in collision calculations. The scenario I've been using to learn is an object with a mass of 4000 kilograms colliding ...
0
votes
1answer
78 views

Could a black hole maintain a stable orbit around the Earth?

Could a rotating Black Hole of mass $1.24\times 10^{10}$ kg maintain a stable orbit around Earth, without significantly altering the path of the Earth or Moon? In addition to this, would the presence ...
4
votes
1answer
75 views

How far has Earth moved from its birth orbit?

It says earth is almost as old as 1/3 of the universe's age which would mean 4.5 billion years . So how far has earth moved towards or away from the sun in these 4.5 billion years? Now perfect ...
-1
votes
2answers
162 views

Rotational Torque Versus Thrust on a Screw

We all used screws and tightening them before, but here is my question. If a Thrust-like load behind the other side of the screw can move the screw out (example pushing), then how much force is it ...
0
votes
1answer
61 views

How long time before all the water in a lake has been replaced? [closed]

Studying hydrology, and in that context we've seen some information about lakes and the times it takes for the water to renew completely in them. This got me interested in finding out how this is ...
0
votes
1answer
41 views

How much salt to dissolve in water for a noticeable change in volume?

I am reading through this High School science lab about how dissolving salt changes the volume of water: Place 300 to 400 g of salt in the flask (1L) Pour in enough water to cover the dry salt, and ...
20
votes
4answers
7k views

Can lasers lift objects?

I have been fascinated by a very intriguing question - Can lasers push objects up? I have done the below math to find out Lets say we have a $1000~\text{mW}$ laser and we would like to lift an ...
1
vote
0answers
24 views

Electro magnet strength to weight ratio

I was wondering. How would I work out how strong a magnet would have to be to support my weight.
0
votes
3answers
147 views

Why can't space become fuel for spaceships? [closed]

I read somewhere that space is constitued mostly of hydrogen. So why can't space and its constituants (not only hydrogen) serve as fuel for future spaceships? The dreamer I am simply imagine a ...
4
votes
1answer
109 views

From how far away could Earth's telescopes detect Earth like radio signals?

The Earth has been broadcasting human generated radio signals for about 100 years now. If a nearby civilization were broadcasting similar radio signals, could we detect them with our own radio ...
0
votes
1answer
50 views

When did the universe become lighter than water at 1 g/cm3 [closed]

Did the universe become lighter than water before light could travel through it? What temperature was it at the time where matter was roughly 1g/cm3?
4
votes
2answers
78 views

If we increase the mass of a black hole by a factor of $k$, by what factor will the surface area of the event horizon change?

If we increase the mass of a black hole by a factor of $k$, by what factor will the surface area of the event horizon change? Given any number of identical black holes each with mass = $\mathrm{m_0}$ ...
1
vote
1answer
47 views

Small enough planet to notice rounding

This is my first question on Physics StackExchange, so bear with me. I am wondering. How dense would a planet need to be for a human to notice the fact that the planet is not flat, but round, by ...
1
vote
1answer
31 views

How can you calculate the thrust-to-weight ratio of a gun?

Is there some formula I can apply to the weight of a gun, along with the force of thrust it creates, and calculate if it will be able to lift itself off the ground or not? Without actually handling ...
4
votes
2answers
1k views

Does surface tension play a role in planet's shape?

I'm thinking that when the planets and stars were forming along with gravity surface tension also could have played a role in making them spherical. Am I correct?
0
votes
1answer
52 views

Spacetime Mercury vs Earth

What is the time dilatation of the planet Mercury compared to Earth? Can a person survive on the dark side of Mercury in the In the L2 position to Mercury and the Sun?
3
votes
3answers
156 views

Can humans control rotation of the Earth?

I'm a class 12th student and this thought just struck me from nowhere. Assume a situation where every human on this planet turns towards west. All of them start walking simultaneously in west ...
1
vote
1answer
65 views

How much energy is released by an evaporating black hole in the last second of its life?

From what I understand, due to Hawking radiation, black holes lose mass in the form of energy (electromagnetic radiation), with these characteristics: The larger the black hole, the less energy it ...
3
votes
1answer
66 views

Is it possible to 'push' a path to the Earth's core?

This may very well be a question for Earth Science SE, but as it is very hypothetical, maybe pure physics is more appropriate... Question: Imagine we have have a wedge that tapers down into an ...
6
votes
2answers
322 views

How much upward force due to ground vibrations does the Earth exert on you?

Say you're walking by the highway and you can feel the vibrations of cars moving along. How would you approximate the force that the ground is exerting on your feet due to these vibrations?
5
votes
3answers
229 views

How would we estimate, ahead of time, “the chances” of LIGO spotting black holes colliding in the period that it has been operating? [duplicate]

Can anyone summarize calculations that have been done about the theoretical probability of a detectable black hole collision happening in the observable universe within the time that LIGO has been ...
0
votes
1answer
78 views

What effect would GW150914 have had over a much shorter distance? [duplicate]

In the wake of the recent news of the confirmation of the existence on gravity waves, I was discussing gravitational waves with a friend, and he asked whether this could potentially lead to some kind ...
-1
votes
1answer
68 views

If the Earth were a pool ball, could I feel mountains? [closed]

If the earth (12,742 km diameter) were scaled down to the size of a pool ball (61mm diameter), the mountain ranges would still exist, obviously. But would a typical human be able to feel those ...
1
vote
2answers
126 views

Let's consider a sphere of radius $R$ at $T_0=100$ C in a far field of water with temperature $T_\infty=30$ C [closed]

Let's consider a sphere of radius $R$ at $T_0=100$ C in a far field of water with temperature $T_\infty=30$ C. How to calculate the sphere's temperature in each "layer" at any time? I really don't ...
-2
votes
1answer
84 views

What's the formula for the speed of an accelerating car?

I am trying to find a formula that closely describes the speed of an accelerating car over time. I have found many graphs on the internet, but so far no formulae to generate them. For my purposes I ...
1
vote
1answer
72 views

Cesium-137 From Fukushima Meltdown

I've been reading up on the Fukushima nuclear meltdown and its effects it had on the environment. The iodine-131 initially released from the incident decayed after 8 days, but other isotopes such as ...
4
votes
4answers
554 views

Would a neutrino bomb do anything? Or can weak force kill you?

In a disreputable animated cartoon (I accidentally watch every episode of religiously), a mad scientist plans on killing all humans with a Neutrino bomb. From context, this is a bomb that produces a ...
11
votes
3answers
448 views

What is the safe distance to a supernova explosion?

In other words, what stars near the Sun may have an impact on the Solar system equilibrium or the Earth life if they become supernova ? Is SN 1987 A too far ?
1
vote
2answers
72 views

Misunderstanding about Reynolds number

I am confused about Reynolds number. I am trying to use the formula to see if NASCAR cars have laminar or turbulent flow. But I am not sure how exactly to use the equation in order to do such ...
4
votes
3answers
108 views

What influence has the distance of the moon on the height of the tides?

As the Moon recedes from the Earth, are the tides getting taller or shorter? If the Moon is, someday, twice as far from the Earth, how many high tides will be there be each day?