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1answer
51 views

Reduction of Earth's Rotation due to increase in humidity

I came to know that, moon is moving away from earth, resulting reduction of Earth's rotation. Similarly, if Earth's humidity increases, water vapor will be move up to the air from water sources, will ...
0
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1answer
37 views

Estimate the amount of atoms in the smallest speck of matter you can see with the naked eye [closed]

I am currently working through a physics text book at my own pace on Newtonian mechanics. I came across this question in the the chapter 1 problems and had a bit of trouble with it. My biggest issue ...
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0answers
45 views

How much wind power is needed to lift someone up? [duplicate]

I'm talking about fan wind power. A range would be sensible from about 8yrs-50yrs as not all human beings are the same weight with the added weight of a 5kg engine and average skateboard.
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3answers
107 views

Is it possible for man to break Earth into 2 parts? [closed]

Many countries have extreme devastating nuclear weapons. Also they have weapons in very large numbers. I want to ask that Is it possible for man to break earth into 2 parts with the help ...
0
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1answer
45 views

Terminal velocity of a steel ball in water [closed]

I am investigating on the terminal velocity of steel balls moving in water. I used the balls with different diameters, such as 3.17mm, 6.02mm, etc. And I used a full-filled 1L graduated cylinder. I ...
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1answer
29 views

How much energy is saved when using luggage with wheels? [closed]

How much energy is saved when using luggage with wheels as opposed to carrying the luggage? Thanks.
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1answer
71 views

Could one fire a bullet with sufficient speed to leave the Earth?

Consider a gun or rifle fired directly upwards. My original question was what speed would be required to escape the Earth. The escape velocity from the surface of the Earth is the classic $$v_e = ...
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0answers
43 views

Vehicle Driving off Cliff (Thelma and Louise movie)

What is the slowest speed at which a vehicle driven off a cliff can clear the cliff without catching its underside between the wheels? In the usual frictionless vacuum, this would appear to depend on ...
7
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1answer
113 views

Is it possible to remove the last block from a the lowest layer of a Jenga tower?

A while back, my brother and I had a discussion about the possibility of removing the last block from the lowest layer of a Jenga tower with the layer immediately above it having only one block in it ...
3
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1answer
92 views

Possible to make full loop on a swing only by “pumping legs”?

Is it possible to make a full $360^{\circ}$ loop on the type of swing in a children's playground if I power the swing only by "pumping" my legs? i.e. nobody pushes me?
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1answer
42 views

What is the acceleration due to Earth's rotational and orbital movements?

What are the accelerations due to earths spin and orbital motion around the sun? It must be negligible otherwise humans would have been feeling it, are there any instruments that can measure it? would ...
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1answer
37 views

Calculating time dilation

I'm writing a science fiction story where the protagonist's experience requires long intervals between events. My plan is to put him/her/it on a spaceship between events at an appreciable percentage ...
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0answers
29 views

Determine the amount of energy used for baking a cake

Let's suppose we have a room of temperature $T_0$ with an oven of volume $V$, both filled with air of density $\rho$ and specific heat $c$. We need to bake a cake in the temperature $T_1$. Thus we ...
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0answers
19 views

What is the change in PSI of a football with 13.5 at a temperature of 77 degrees F when placed in a 23 degree environment? [duplicate]

The internal pressure of a regulation football is 13-14 lbs/square inch at 77 degrees (Fahrenheit). What pressure will it become when taken out of that 77 degree environment and placed in a 23 degree ...
8
votes
2answers
649 views

Is it possible to produce gravitational waves artificially?

Why don't they make a ball with irregularities, say the size of a tennis ball, then spin it very rapidly, so it would produce gravitational waves like a spinning star with irregularities on it? Is ...
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2answers
43 views

Torque (in $Nm$) of a cyclist

We're discussing bicycles with a friend, and it came to safety, speed and power. Now the question we have is: how much torque do my legs provide to the bicycle? I'm no expert in physics sadly, and ...
0
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1answer
54 views

How many coils of a wire in an electromagnet would make 100 milliTeslas field? [closed]

This is a rather stupid question. I'm making a basic electromagnet using copper wire and an iron nail and need to make an electromagnetic feild roughly about 100 milliTeslas . Ill be using a gauge 6 ...
2
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1answer
47 views

Finding the expression for the time it takes for a water tank to be half empty

The problem is to find an expression for the time it takes for a cylindrical water tank is half empty. I am given that the water tank has a diameter of $D_0$ and a hight $H$. The water outlet is ...
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3answers
439 views

How hot can metal get in sunlight? [closed]

I will make some 5mm blackened steel letters for a building. Now, in the sunlight in summer, how hot can they get? EDIT: i want to place some LEDs on the back of the letters. now the question is if ...
3
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1answer
299 views

Calculating Kryptonian speed in the movie “Man of Steel”

This is my first question, so I'm not sure if this is the right place to ask but: How would you go about calculating the speed of Kryptonians in the movie Man of Steel (2013)? Specifically, I'm ...
0
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2answers
52 views

What should the length of my wire be in order to get a surface area of 10cm^2?

I would like to make a flat coil out of a steel wire that is $1.22 ~\text{mm}$ in thickness (or $1.22~\text{mm}$ in diameter). I wish to make the coil up the wire into a flat disk that has a surface ...
0
votes
1answer
22 views

An example on computing the density of a typical nucleus

An example from my text is as such: Compute the density of a typical nucleus, and find the resultant mass if we could manufacture a nucleus with a radius of 1cm. I will only provide a partial ...
13
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1answer
300 views

How hot would tritium water be?

I realize this is kind of a silly question, but if you have tritium water, with the tritium half life of 12.5 years, I expect it would be quite hot. (note, this is not a homework question, I'm just ...
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4answers
358 views

Dodging paintballs

I was recently watching The Matrix, and was considering the speed at which one needs to move to literally dodge a projectile. Now, in real life, it is impossible to dodge bullets as such a feat would ...
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2answers
55 views

Do inelastic or elastic collisions have any effect on a large bodies movement (like the Earth)

Recently read a question regarding the temperature of the CMB & one of the comments got me thinking... From what I understand, collisions between subatomic particles and objects out in ...
2
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1answer
110 views

When will the Earth stop rotating?

I looked up leap second in Wikipedia. It is a second added (usually) to clocks to keep them in sync with the atomic clock. It said that 25 leap seconds were added in the last 43 years and that none ...
3
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3answers
143 views

Does my (too low) tire pressure, affect the speedometer of my car?

Does my (too low) tire pressure, affect the speedometer of my car? How big is this effect?
0
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0answers
26 views

Thermistor calibration - estimation of number of reference temperature points needed

A thermistor changes resistance with the temperature in a non-linear way and follows the exponential Arrhenius equation. Two reference points, ice slush water and boiling water, are used for ...
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votes
5answers
4k views

Why don't things get destroyed by gas molecules flying around?

Gas molecules go at an insane velocity, and though they are miniscule, yet there is a LOT of them. Of course, because of all these molecules hurtling around, there is air pressure; yet if you envision ...
0
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2answers
75 views

What is the pressure of falling water?

Imagine a breaking wave 10m high. The wave breaks onto a beach. What is the maximum pressure created by the wave on the beach, ignoring effects such as might be cause by air?
2
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1answer
59 views

What are the tidal effects of Io on Jupiter?

I recall reading an essay by Asimov (I think) around 1980 stating that the tides are a function of a power of the diameter of the primary, so (surprisingly) small close moons of Jupiter raise large ...
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1answer
140 views

Stone vs. Atomic Bomb

What would do more damage, a B53, a 9 megaton uranium bomb, or a medium sized stone (2 kg) stone throw at 90% the speed of light. One thing that I know that will have to be considered is that fact ...
1
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1answer
139 views

How many electrons are there in the universe?

Someone on io9 estimated there were about 10^80 electrons in the universe, but I want to ask the Stack Exchange physics community.
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2answers
57 views

Is it possible to calculate the radius of star?

Suppose I know the Luminosity $L$, temperature $T$ and Mass $M$ of star. Assuming the star is very heavy so that we can treat it to be radiation-dominated star. This would imply that pressure inside ...
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1answer
102 views

Largest size of a low gravity, Earth-like planet with Volcanoes and Earthquakes?

Provided that the Solar System consists only of Sol, a planet, and the planet's moon.... How large can my planet be so that it has low enough gravity that teenage human girls trained for jumping, are ...
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2answers
103 views

Atoms in a piece of paper?

How many atoms are there in a common paper sheet? I mean, for example, in one of those we use for photocopies, numerically speaking, how many atoms in total? (Ten to the power of..?) And I'd like to ...
0
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0answers
58 views

Orbital elevators and the Coriolis effect

Consider an orbital elevator simply modelled as a large mass in geostationary orbit (altitude approx 36,000km) around the Earth, connected to a point on the equator via a strong, light, likely ...
1
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1answer
125 views

Continuity equation and pressure head in a tank

Consider a tank which is full of water. We connect a horozontal pipe at its bottom. When the pipe is open, water starts flowing through the pipe, then the velocity of water is proportional to the ...
1
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1answer
22 views

Stair well descent

I am trying to understand the science behind lowering a person down a flight of stairs on a sled. My tensile strength only says it can hold 250 pounds but I have seen it lower people that weigh 300 ...
22
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5answers
8k views

Is it possible to shoot bullets in space or would the recoil of the gun be too strong?

I've read a few articles that say that astronauts have already brought guns in space and that shooting bullets in space is possible. But won't the recoil of the gun be too strong? Law of ...
5
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3answers
166 views

What would it take to cause lightning to jump between the Moon and the Earth?

This question comes from @Floris' speculation at the end of his excellent answer about what it would take to kill everyone on the Earth with electricity. Doing all this in 1/10th of a second ...
3
votes
1answer
98 views

Force and lions

Alright. So me and some other people right now need an answer to this. If you have 1 trillion lions traveling at 81 kilometers (top speed of a lion) towards the Sun in a pretty dense ball. (As dense a ...
29
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5answers
5k views

If the Earth is a good conductor of electricity, why don't people get electrocuted every time they touch the Earth?

Since the Earth is a good conductor of electricity, is it safe to assume that any charge that flows down to the Earth must be redistributed into the Earth in and along all directions? Does this also ...
1
vote
2answers
70 views

What should we do If we wanted to increase the angular velocity of a planet? [duplicate]

We could hit it with really fast objects, but could we manipulate the orbit of a large satellite to speed up its rotation? What would be the easiest way?
1
vote
1answer
24 views

Tangent and Normal accelerations position estimation

How can I derive a particle position given it's last known positions (x,y), velocities in it's components (vx, vy), tangential and centripetal (normal) accelerations? (this is the only available data) ...
1
vote
1answer
35 views

Tsunami effects of a nuclear explosion

Sea surface nuclear explosion arouses a tidal wave of water. How does this kind of wave compare to naturally occurring tsunamis? E.g. what would be the potential of a 100KT bomb 100km away the from ...
4
votes
3answers
206 views

What was the amount of energy released in the 9/11 terrorist attacks?

I read somewhere on the internet that the amount of energy released by the terrorist attacks on the twin towers on 9/11 should have been of the order of 100 tons of TNT. This number surprised me, ...
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2answers
44 views

How quickly does a gas reach a uniform temperature in an enclosure?

I'm just looking for ballpark figures and reasoning. Suppose a gas (air) at STP was introduced into a 10cm diameter sphere of infinite heat capacity and conductivity at one degree above the gas. How ...
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2answers
104 views

Would it be possible to make a space elevator only in the atmosphere?

I wonder if with current day technology we could make a "floating platform" which hangs from a satellite by a space elevator. This could allow a "launch process" involving floating a balloon to the ...
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3answers
101 views

How can Denver offer Hot Air Balloon rides?

So the air density in Denver is 1.0 kg/m^3. And heated air has the density of 0.95 kg/m^3. So adding the weight of the basket and balloon I don't understand how a hot air balloon could get off the ...