Question: What would be your goal with strengthen materials because not all things need to be hard?

James Marrow answered on 13 Jun 2011:

You’re right – not all things need to be hard (or stiff) – imaging trying to do a bungee jump with a steel cable instead of a rubber cable 🙂 (both are strong enough to take your weight, but one of them could rip your legs off with the force!)

However, in many engineered structures we need to carry large forces in a small space. That needs strong materials. Strong materials also last longer and are safer. We may only need their strength in case of an emergency. (If you were rock-climbing, who would you rather have holding the rope, your teacher or the strongest man in the world (http://www.ukstrongestman.co.uk/)?)