Flight on Mars

In 2021, it seems like world is under attack of Covid 19 (a virus commonly known as corona virus) and world is completely in chaos. While it seems very convincing but this is not all that is happening in 2021. Mankind has achieved a major milestone in space science. Mankind, who once dreamt of flying in air, was dreaming to fly in atmosphere of a planet other than earth for quite some time but it is 2021 when humans were able to make a flight (man less) in environment of Mars. On 25 April 2021, helicopter managed by NASA made a record of longest flight on mars. It flew 5 meter high and covered distance of 50 meter with speed 2 meter per second. NASA has attempted flights previously but this was the longest flight on Mars. This flight has given confidence to scientists for improved and better navigation across the planet. It has also helped the engineers and scientist to understand environmental conditions on Mars in much better way. This flight has taken mankind one step closer to the dream of visiting Mars one day. There have been talks of leaving earth and go and colonize Mars for ages. There were times when people had suggested to leave this dream and focus on other cosmological projects. But those have believed in this are finally getting something to cheer about. Ingenuity, name of helicopter, made his first flight on April 19,2021. This flight was 10 feet high. After making small distance Ingenuity returned and landed safely. Then it took its second flight and reached height of 16 meter same as high as for third flight. Then it made its last flight which was the longest and record breaking.

We will keep you updated about more progress on this project. In the mean time you share this article with your friends and tell them while you are sitting in room there are preparations being made for your trip to Mars. So be READY.

Carrier Diffusion in Semi Sonductors

 We know semiconductors have conductivity not as high as conductors and not as low as insulators. They have found a large number of application due to this unique behavior. We have categorized them into intrinsic and extrinsic semiconductors depending upon if they are in pure form or contain trivalent or pentavalent impurity. Those semiconductors with trivalent impurity are called as p type semi conductors and ones with pentavalent impurity are called as n type semi conductors. P type has holes in excess while n type has electrons in excess. We know diffusion is movement of particles due to concentration differences between two points. Particles move from high to low concentration. When n and p types are brought in contact electrons move from n side to p side due to concentration difference. Similarly holes move from p to n side due to concentration gradient. This happens due to thermal energy of electrons which exhibit itself in the form of kinetic energy of electrons. This diffusion leads to formation of depletion region in such materials.

For more understanding and short video explanation of charge carrier diffusion 

Click here for short video explanation.

What is Drag Force?

 When we were children, we always enjoyed pulling our hand out of window of car and experiencing air exerting force on our hand. We have also liked the scenes from action movies where heroes have their hair flying backward in air while running bikes at high speed. Some of us were amazed when they saw men jumping from air planes and coming down with the help of parachute. If you have ever swum in a pond of water, you would have known that moving through water takes a lot more energy compared to moving through air.

All examples cited above involve a special force called drag force. When an object moves through a medium, a retarding force acts on it. This retarding force is called drag force. Drag force depends upon different factors like speed of object, shape of object and nature of medium. Nature of medium is specified by viscosity. Viscosity is a resistive effect offered by medium due to resistance between various layers of medium. More viscous a medium is, greater will be drag force. A higher viscosity and hence greater drag force means greater force will be needed by the object to move through medium. As the velocity or speed of object is increased, drag force is also increased. In order to decrease the drag force and still be able to move at higher speed, objects are designed in special shapes. If we observe a ship and fish we can see similarity between two shapes. Both are narrow at the start and gradually increase in with. This is known as streamline body shape. Transporting vehicles on land, in air or water are designed while keeping this property in mind. This type of designs help in enhancing speed with greater stability and lower fuel consumption. For an object of spherical shape and speed v drag force is F=6πηrv. This relation is known as stoke's law.

In winter season, fog is a great example where we can observe drag force in action. Fog consists of tiny water droplets falling from high altitudes. As the fog droplets start falling down towards earth in air (medium of movement), air offers drag force to droplets. As the time passes, speed of fog droplet increases due to gravitational acceleration. As mentioned above, increase in speed increases drag force hence retarding force also act on fog droplet in addition to gravitational force. Hence speed of fog droplets depends upon net force and not only downward gravitational pull. For most droplets, weight i.e gravitational pull becomes equal to drag force. At this stage, net force becomes zero and hence droplets fall with constant velocity. Usually this velocity is very small and hence these droplets appear to be at rest. Due to this a large number of water droplets gather in air and we can see these droplets as fog. The constant velocity with which these droplets come down is known as terminal velocity. In coming posts we will discuss terminal velocity in detail.

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