A worker knocks on one end of a long steel rail…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A worker knocks on one end of a long steel rail. A friend puts an ear to the other end, away. The sound travels through the rail at and through the air at . After how long does the friend hear each sound, and what is the gap between them?
Need a reminder? The key ideaShow
Speed . Sound travels at about in air, in water and in steel. In air, with in .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Rail. .
Step 2. Air. .
Step 3. Gap. .
Answer: two knocks: the first after , the second later.
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