This is one of my Doctoral assignment from Current Science and Technology in Japan Course which has never been published anywhere and I, as the author and copyright holder, license this assignment customized CC-BY-SA where anyone can share, copy, republish, and sell on condition to state my name as the author and notify that the original and open version available here.
1. Why do we need high strength metals for making a new car?
- To protect the driver and passengers from external force (safety).
- To reduce the weight of the car (light weigth).
- To maintain the form of the car, for example there are mechanics and engines that produces heat.
- The car must be strong enough to handle its internal force.
2. You are going to pick up “Treasure box(500kg)” at bottom of deep hole (5000m in depth). You have a long steel wire with 30kg/mm2 of strength, 5mm of diameter and 10000m of length. Can you pick up the box, or not? (If you couldn’t pick up by using the steel wire, what type of wire to get to pick up the box?)
- Load = 500kg
- Rope = 10000m
- Depth = 5000m
- Number of ropes available = absolute(Rope/Depth) = abs(10000m/5000m) = 2 : We can use 2 ropes of 5000m
- Rope Diameter = 5mm
- Section area = πd2/4 = 3.14*25/4 mm2 = 19.64mm2
- Total Section Area of 2 ropes = 19.64mm2 + 19.64mm2 = 39.28mm2
- Stress = Load / Total Section Area = 500kg / 39.28mm2 = 12.73 kg/mm2
- ? 2 Steel Wire Strength > Stress, ? 30kg/mm2 > 12.73 kg/mm2: TRUE
- Answer: yes, the available steel wire is able to retrieve the treasure.