Physistri

Here on Earth we see exactly the same features of the moon’s surface because the moon spins once around its axis.It spins in the same amount of time it needs to orbit the Earth,which is about 27.32 days. 

As we know that in newtonian (Newtonian) physics, gravity is a force between two objects with mass. F=Gm1m2/r2, if m1 is your mass,m2 is the mass of earth or moon and r is the radius (distance between forces ) of the earth or moon or other planet. When the ratio m2/r2 increases the force of gravity increases.Now, if we take mass of Earth m2E=5.97*1024 kg and its radius is rE=6378 km…. after calculation FE=9.8m2 N .For moon, m2M=7.34*1022 kg and rM=1737.4 km and after calculation F=1.62m2 N .The pull of gravity on you on earth is greater than on moon a nutshell less gravity is due to less mass. According to Einstein gravity is the curvature of space-time created by massive objects.Greater the mass is greater the curvature more the pull.

Why do some metals go rusty ?  Iron and steel rust when they come in contact with water and oxygen.When water hits iron for example it reacts with carbon dioxide (CO2) in air to form carbonic acid, then iron is dissolved.Some of water will break into its component oxygen and hydrogen.This oxygen reacts with dissolved iron to from iron oxide . Iron oxide is rust. 

Like we said in the previous question that every year is divisible by 4 is a leap year.But 1700 , 1800 and 1900 are divisible by 4 and not leap years. because of the earth needs exactly 365.242199 days not 365.25 to  orbit the sun.So,a year is a leap year if it is not only divisible by 4 but also by 400. 

Why do we have a leap year ?  A year is the time it takes Earth to orbit the sun.The calendar is divided into 365 days .It takes for the Earth to orbit the sun not exactly 365 days but about 365.25  days. So,every four years we throw in an extra day. 

What makes ice slippery is the water layer on its surface.The cause of this water layer is the pressure applied by the skate,the pressure increases the melting point of ice causing the outermost layer to melt.And  after the skate would slide across,a sheet of water would refreeze again as soon as the skate passed.Another scientists claim that the reason is friction between the skate and the ice.The friction generates heat that melts outer layer of ice. 

The story starts with the sun,in some  places where the magnetic field is very high  it pushes itself out of the surface via plasma(ionized gas).When several tons of  plasma leaves the sun it is called solar storm.The storm continues its way till it becomes close to the Earth’s magnetic field.Therefore,The magnetic field of Earth  deflects the storm by coupling together(see image below).What happens is that the electrons from the solar storm interact with the Earth’s atmosphere following the field lines to north and south poles.Again,the interaction of electrons with the gas  atoms causes them to release both light and more electrons.

The Earth has its own magnetic field , it acts like there is huge bar magnet buried inside,but this bar magnet is not on the earth rotational axis it is shifted by some angle.The south of the bar magnet is on the magnetic north and the south polarity is on the magnetic north(image).As opposite polarities attract the magnetic needle (north) is attracted to the south polarity in the magnetic north.That’s why the needle always points north.If you want to know “why earth has magnetic field?”go to letter E.

Before Galileo it was thought that heavy object weighs more.So it must fall down,since it has more weight (greater downward force applied to it). But that was proved wrong when Galileo threw two balls of different masses from Pisa tower.Where the  heavier object get more mass that means it gets more inertia (more resistive to move).Hence,it needs more gravitational force (weight) to accelerate it at the same rate as the light one.

We get sun heat via radiation,so most people wonder why mountains are colder than valley,while mountains are closer to the sun.They are indeed correct since radioactive energy decreases with distance from the source.But the sun is over 150 million Km away and the difference between the highest mountain (Everest)and the lowest desert is 8000 m which is negligible compared to 150 million km.Therefore, it is not the distance!. It has to do with the pressure.The pressure is low in the mountains(thin air/less molecules) and higher at the valleys(thick air/more molecules).Where denser thick air can store more heat. As we go up a mountain, the air becomes less dense and less heat can be absorbed. But something else is going on. As we know the warmer air rises up(since it is less dense)while the colder air stays down,so in the process where the hot air rises its temperature drops down since it lose pressure(gas law).By the time the air reaches the high mountain it has lost a lot of pressure an...

When we want to speed up an object we give it energy. As special relativity tells us energy and mass are equivalent(E=mc2).Then some of this energy is transferred into mass, increasing the rest mass.

Actually this technique is based on a physics concept called center of mass.A center of mass is a point not necessarily inside the body-where the whole mass of the object is concentrated.We human have a center of mass, when stand up the center of mass is around the belly. It moves all the time according to how our body is positioned even it can be outside our bodies.The jumper runs very fast so he can divert his horizontal velocity to vertical velocity and jump.When he jumps backward above the bar his center of mass becomes below his body.If he was not jumping backward he has to apply more force to lift not only his body but also his center of mass.

The motion of any object depends on the motion of the observer since motion is relative.If we have many observers,each one measures certain velocity relative to (compared to) the frame of reference that objects are standing in.When you are in the car it is at rest relative to you and if the car is moving with a ‘constant speed’ your brain can hardly tell that the car is even moving on the road. So relative to me the road,trees and the power lines will be moving with a speed equal to the speed of the car and the car is at rest.

Water ,unlike most liquids , its volume expands when passing from liquid state to solid state.Due to hydrogen bond that makes water so special.Water has enough energy for molecules to move, but when it reaches 40C the atoms slowdown to form this hexagonal form (see image).Where it forms solid crystal structure that takes up more room(space) than water.

The reason of why things float in water;(can be applied to air...) applies to air as well. Helium and the balloon displace an amount of air,and as long as Helium is less dense than air.Air contains oxygen and Nitrogen that are much heavier and have larger molecules than that of Helium.Then,the weight of the displaced air is more than the weight of helium and the balloon introduced.Hence,the balloon will float in the air(this is the law of buoyancy).

There are reasons for why roads are black in colour that I identified and I want to share with you :- Asphalt concrete is available at a low price. The cost that occurs to made of asphalt roads is also low. During the summer and high temperatures, the black color does not reflect the solar waves that will help us to see the roads clearly. Asphalt concrete absorbs heat but that doesn’t affect visibility in extremely hot conditions. In night times bright colors can be easily seen on black roads. whereas bright colors on white roads cannot easily be identified. We can easily say that white lines can be easily identified on black roads whereas white line road markings cannot be identified easily on the white roads. In addition, any irregularity on the road, with the exception of the black color, can be simply detected.

Metals are conductors of electricity,and as known conductors have free electrons.Each electron acts as a bar magnet and it has a north and a south pole.When we put the metal next to magnet,the tiny magnets(free electrons)all line up in a certain way that they are attracted to the magnet.For example,if I approach the south pole of a magnet to a piece of iron,the tiny magnets(free electrons) in the iron piece will line up where all the north poles face the south pole of my magnet.And unlike polarities attract. Something to know:If you want to know why electrons behave like tiny magnets you might ask why they are charged in the first place .Actually no one knows!.

It is curious that human swing their arms as they walk.That is, your right arm swings forward when your left leg steps forward and vice versa.The first reason is that we swing our hands naturally because it takes less exertion than when holding the arms down.Also,swinging arms in an opposing direction reduces the angular momentum of the body, balancing the rotational motion produced during walking . To explain ,during a step your legs try to make your body spin about a vertical axis but swinging your arms cancels this out.

The answer for this question is somehow similar to the answer of the question "why is bubbles round?" ,that’s how nature works.Earth and other planets are spherical since spherical shape has lowest energy a material can be.Due to the gravitational force that pulls the masses together equally in all directions.The stronger the force of gravity is more spherical the shape becomes.That is why mars has larger mountains than Earth (force of gravity of mars is weaker) .Moreover,as long as the maximum mountain size is small compared to the radius of the planetoid the body will be spherical. Note: Earth is not perfectly a sphere , it is approximately spherical .

Clouds become electrically charged,the upper portion is positively charged and the lower portion is negatively charged.There are many explanation for how the cloud acquire charge,the best explanation is that electric charge is due to the collision between ice,water and water vapor. When the electric field in the cloud increases and increases,electrons in the cloud start to repel electrons in the ground surface causing it to become positively charged.Now,we have negative charge - air-positive charge (see figure),but air is an insulator and the lightning needs a path,here comes air ionization process where air become ionized .Then what’s called a stepped leader which is an invisible discharged path that moves downward from cloud to ground.And another leader is then created upward from Earth to cloud.When both make contact visible lightning occurs.

The scientific name for the twinkling of stars is stellar scintillation.The light of the star is bent(refracted)many times and in random directions from moment to moment because light passes down through many layers of air and each layer has different temperatures,pressures, densities and other factors.Each layer will bend and affect light in a certain construction from our perspective the light will appear in a location then after millisecond it will appear in other location and this seems like twinkling.

We see a rainbow when the sunlight hit the right droplets that are just in the right place to hit our eyes.While,other droplets send their sunlight somewhere else.But we actually don't see a full circle because the earth gets in the way.Moreover,the closer the sun is to the horizon more the arc we see.

Just like an airplane there are four forces acting on the kite:upward force (lift),downward force (weight), backward force (drag) and forward force (thrust).The left is an upward force that pushes the kite up since kites are shaped so that the air moving over the top moves faster than the air moving over the bottom to make the pressure below the kite more than the pressure above it.The weight is the downward force due to gravitational attraction.The thrust is due to wind while the drag is due to friction. To launch a kite into the air the force of lift must be more than the weight. To keep a kite flying steady the four forces must be in balance.

The earth is rotating at a very high speed around itself(1000 miles per hour)and around the sun(67000 miles per hour).But,we don’t feel the motion when things move at constant velocity.For example,if you are in a car and it is moving with constant speed and you close your eyes not to see things outside moving you feel that you are stationary (That is what we call relative motion) and so is Earth.Though there is an outward force pushing us away from earth due to itsrotation,gravity over comes this force.We can only feel its rotation if Earth changes its speed increasing or decreasing.

Mars is called the red planet.The reddish color is due to the rust on its surface this rust is iron oxide. Iron oxide (rust) is formed due to the reaction between iron and water.But there is no water in mars!.So scientists proposed that there was water billions of years ago that combined with martian rocks rich in iron to form iron oxide.

There is a relation between the fuel burned and the color.Explanation of it is that electrons in the atoms of the fuel used are excited due to heating (energy).They move from ground state to higher energy level and when they return back they emit photons of different wavelengths.Each wavelength corresponds to a certain color. Sodium emits orange light when burned. If you see blue in wood flames,it is from(not "from" use, "because of") the burning of carbon and hydrogen.Red comes from lithium ,and copper will make green or blue flames when burned.

Light bulb is made up of many part,one of these parts is called the filament.When the electric current(electrons)passes through the filament it heats up.Since electrons increase the kinetic energy of the filament’s atoms which intern increases the temperature. The electrons of the filament atom become excited and move to a higher energy level.When they return back to their initial level they emit photons(Light).

This is due to what we call light scattering(throw in various random directions) where light strikes a particle or a collection of particles,thereby changing its direction.Clouds are made up of water or ice droplets and they are just the right size to scatter all colors of light.When the white light from the sun hits the cloud,water and ice droplets scatter all the wavelength of light in all direction to reach our eyes. Note : But rain clouds tend to be grey that is because the clouds block sunlight due to their thickness.The thicker the cloud,more light it blocks.

The flame goes upward even when there is strong gravitational pull like on Earth.The fuel reacts with oxygen to release heat and other gases.The released gases are hotter than the surrounding air.This means that the obtained gases are denser than air,so an upward buoyant force pushes the gases.Applying Archimedes principle : A force equal to the weight of the air displaced lifts up an object surrounded by air.When we are talking about weight we conclude that gravity is the reason for the flame shape and without it hotter gases won’t move upward.

It goes to the formation of the solar system(as we explained in the previous question).The solar system formed out of a clump of gas and dust.Then gravity collapsed this clump of gas and dust in the direction of its axis(that takes less energy).Thus the cloud become a spinning disk,then planets formed out and kept located in the same plane till today.And due to the conservation of angular momentum they keep orbiting in the same plane.

As Earth is rotating around its axis,the moon having a gravitational pull on earth’s oceans and some of the crust below(moon arises tides on the earth).It turns out that the moon attracts the ocean tides.Roughly every 100 years, the day gets about 1.4 milliseconds,or 1.4 thousandths of a second, longer.But this is a small effect because the tides aren’t very high and the moon is very faraway.

Most people will answer that they are weightless because there is no gravity,this answer is wrong !.Space stations are very close to earth and there is a strong gravitational pull on astronauts.The truth is that astronauts have weight butthey feel weightless since they are always falling toward Earth!.To explain the space station and everything inside it is in free fall toward Earth. So they are accelerating toward it, but they don’t crush with it because of their orbit.

Bubbles are made of soap and water,where water molecules contain two hydrogen atoms and one oxygen atom.Hydrogen has positive charge and oxygen has negative charge,this causes water molecules to attract each another giving water a surface tension.Surface tension makes the thin film of soapy water assume the smallest surface area which is a sphere (sphere has smallest amount of surface area and lowest energy).