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Q . How do solar calculators work?
Ans . The claculators of today use miniature electronic circuits to carry out calculations. These circuits are normally provided with electricity from battery cells. In a solar calculator, the electricity is obtained from sunlight through photovoltic cells. These cells have thin slices of semiconductors. The surface facing the light gets positively charged and the other surface becomes negatively charged. Thus they make up the battery terminals for the flow of electricity. Q . Why does an iron ball sink but not an iron ship? Ans . Any object kept in a fluid, is subject to an upward force or pressure, that is the buoyancy force exerted by the fluid. The famous greek scientist, Archimedes, discovered that this force is equal to the wieght of the volume of the fluid displaced by the object. If the weight of the object is more than the weight of the water displaced, it sinks into the water. If both these weights are equal, the objects floats in an immersed position. However, if the weight of the object is less than the weight of the water it displaces, the object is pushed up above the surface of the water till weight of the water displaced by the portion of the object remaining below the surface equals the weight of the object. Following this principle, the bottom portion of the ship is made hollow so that it can displace a large volume of water, so large that the weight of the water displaced is equals the weight of the ship along with its load. A solid iron ball sinks but a hollow iron ball of equal size. i.e. having the same volume but less weight may float. Q . Why do we use two sails in a sail boat? ANS . In order to move in our desired direction, we use two sails in a sail boat. One sail is used to catch the wind and reflect on the other. The other sail is faced to our desired direction with the aid of an instrument called Rudder. When the wind falls on the other sail (which is facing towards the desired direction), it exerts pressure on the other sail. Due to this pressure the boat proples in the desired direction. Q . How do we get photos from negatives ? Ans . When a photograph is to be printed the negative image is first made into positive image. This is done by pressing the negative tightly on a paper which has silver salts. These slats turn black on exposure to light. When light is passed through the negative to this paper a chemical change takes place on the paper. The light areas of the negative will transmit more light than the dark areas of the negative. The negative image is reversed on the paper, which is then fixed using a solution, usually sodium thiosulphate. This washes away the unexposed silver salts on the paper. After washing with water and then drying it, the photograph is ready. Q . How does thermos flask keep a hot drink hot and a cold one cold? Ans . A thermos flask is basically a double container where space between the walls is kept under vaccum and outer surface of the walls are kept shiny and smooth so that they act like mirrors. The vaccum prevents the flow of heat through the walls by conducton or convection, the process which require some medium. Heat transfer by radiation can take place through the vaccum, but the radiation heat is reflected back by the mirrored surfaces. So, not much heat can flow throught the walls of the flask and your drink remains hot or cold as desired. Q . Why does the heart beat faster ? Ans . The heart beat faster during and after exercise. This is because during exercise the amount of carbon dioxide in the blood increases. To take the carbon dioxide out of the body the rate of breathing increases. Simultaneously the heart beat increases to speed up the circulation so that the blood can carry carbon dioxide out and bring in oxygen at faster rate. Q . How Does Artificial gravity Work? Ans. Spinning creates centripetal force, which increases with faster spin rates. A popular amusement park ride consists of a cylinder that spins around a vertical axis. People stand with their backs to the inside wall and the cylinder spins up. Once it's going fast enough, the floor drops away and everyone is stuck to the wall by the artificial gravity. What's really happening is that the cylinder wall is exerting a force (centripetal force) to keep everyone moving on a curved path (in this case, a circular path). But to the people or any other object in the cylinder, the effect is the same as if there were a force pushing them outward (called the centrifugal force) -- that's the artificial gravity. Q . Why does the gun recoils? Ans . When a bullet is fired from a gun, the force sending the bullet forward is equal to the force sending the gun backward. But due to high mass of the gun, it moves only a little distance backward and gives a backward jerk or kick to the shoulder of the gunman. The gun is said to have recoiled Q . How does a blanket that keeps us warm in winter also keep ice from melting ? Ans . A blanket and similar woolen garments are bad conductors of heat. This means they do not allow heat to be transferred easily. When you wrap yourself in a blanket in cold weather, the blanket prevents your body from shedding its own warmth. So you feel warm and snug inside a coat or a blanket. However, if you keep ice inside a coat or a blanket, the blanket blocks the warm air outside from coming in and causing the ice to melt. Q . How Do we Walk? Ans . When we walk on the ground our foot pushes the ground backward, and in return, the ground pushes our foot forward. The forward reaction exerted by the ground pushes our foot forward. The forward reaction exerted by the ground on our foot makes us walk forward. if however the ground is slippery or if there is all ice, it becomes very difficult to walk. This due to the fact that on the slippery ground or ice, The friction is much less, and we cannot exert a backward action force on a slippery ground or ice which would produce a forward reaction force on us 
Q . Why the gun recoils? Ans . When a bullet is fired from a gun, the force sending the bullet forward is equal to the force sending the gun backward. But due to the high mass of the gun, it moves only a little distance backward and gives a backward jerk or kick to the shoulder of the gunman. The gun is said to have recoiled. Next>> Return to Common Teasers In :- �
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