Answer to Question #291674 in Physics for SelMel

Question

One-meter-long coaxial cable is incorrectly connected to the output device, so part of the signal bounces back on the connection. Determines the speed of the signal along the wire if we see echoes in the signal with a delay of 10 ns.

Answer 1

First the signal reaches the other send, which takes time t, then the signal is reflected and moves back to the input at the same speed, which, obviously, takes the same time. Therefore, the time in one direction is 5 ns. Divided by 1 m, it gives

$$v=\dfrac 1{5·10^{-9}}=2·10^8\text{ m/s},$$

which is about 67% of the speed of light.