|MadSci Network: Engineering|
Question (a): What is the difference between "Compression" and "Tensile Strength"? Comment: I have to limit my explanation to your level of understanding since you are a third grade student. Answer (a): When you throw a ball or land a punch on an opponent, you are applying or using force. Force is an interesting subject but we wouldn't get into this subject but the word 'force' will be used to explain some theories behind your questions. COMPRESSION: When you push on both sides of a spring or sleep on a spring bed, you are applying a force that is due to compression. On the other hand, if you pull on both sides of the spring you applying TENSION force. TENSILE STRENGTH: If you pull on a spring up to the point that the spring breaks, then the force applied to the point of failure is called TENSILE STRENGTH. In order word, the force applied to the spring up to the point of failure (break point) is called TENSILE STRENGTH. Answer (b): STRESS: Have you ever been under PRESSURE?. Engineers in the areas of Civil, Mechanical, Chemical, and Materials, often used the word "stress" instead of pressure. When you stand on your patio, your weight on a certain area of the patio contributes to the pressure your body is exerting on the area of the patio. Now, if you press hard on the round side of an egg and you press on the cone side of the egg using the same force, which side will break first?. Well, the STRESS (or PRESSURE) on cone side of the egg is going to be larger than the round (circular) side. DO YOU AGREE WITH THIS STATEMENT?. I HOPE SO. Let's discuss this a little bit further. Remember that STRESS is defined as FORCE DIVIDE BY AREA. Remember the area of the cone side of the egg is approximately half the area of the round side, therefore the STRESS required to break the cone side under compression is twice as large as the stress required of the round side. The round side, under compression and for the same force, will break first before the cone side. Likewise, if you have a boiled egg which usually have void (air space) on the round side of the egg, breaking the round side of this boiled egg is faster that the cone side. Why? (1) Requires minimum stress on the round side compared to the cone side and (2) the contribution of the air space (void) inside the boiled egg. Answer (c): EQUATION FOR STRESS: FORCE/AREA, that is, Force divide by area. Force is mass multiply by gravitational constant and Area is length multiply by width. The quantity scientists used to describe force is pound-force ( or KILOGRAM FORCE) and for area, square feet (square meter). Goodluck to you as a future Engineer and God Bless.
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