Tutor profile: Khandakar R.
Subject: Physics (Waves and Optics)
Do you know how infrared was discovered?
Infrared or IR, is electromagnetic radiation with longer wavelengths than those of visible light and is therefore invisible. In early 19th century, William Herschel, an astronomer used a prism to refract light from the sun in order to measure the temperature of each color of light. So he put one thermometer in each refracted light (total seven thermometers for seven colors) and another thermometer just beside the red light to measure the difference in temperature. After a few hours, he was surprised seeing that the thermometer that was not in any light also changed its reading. And then he figured out that there must have been another light of different wavelength which we can not see.
How is the area of an object measured?
Irrespective of its shape, the area of all objects are measured by multiplying its two sides. If you modify the shape of a triangle, circle, trapezoid, sphere, cylinder, cone, you can see the area is just multiplying its base with height.
Subject: Civil Engineering
What are the implications of tension and compression in civil engineering?
Tension and compression are the two fundamental concepts of civil engineering. During the game of tug-of-war, the rope undergoes tension from two opposite teams and if the tension surpasses the rope's ability to handle the lengthening force, the rope snaps. On the other hand, when you push down on a spring and collapse it, you are actually putting compressive force on the spring. The compressive and tensile strength of building materials is of primary importance to architects and civil engineers. Consider a simple structure that consists of two posts supporting one beam. Atop the beam is a very heavy weight (e.g. a stone roof). In order for this structure to be sound, the two posts must have good compressive strength, while the beam must have good tensile strength. Although the beam isn't experiencing pure tensile stress, its tensile strength is the limiting factor in whether it buckles under the weight of the structure above. Prior to the modern age, when it became possible to mass produce steel economically, architects and engineers were limited to materials lacking in tensile strength (e.g. stone, brick, concrete). This compelled the development of arched construction, which converts most of a structure's tensile stress into compressive stress.
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