A wave in slinky travelled two and fro in 10sec the length of the slinky is 10m. What is the velocity of wave?

To answer this question, i.e., to determine the wave's velocity. We will consider the total distance travelled by the wave as it travels back and forth, then apply the values given in the question to the velocity formula to obtain the required answer.

We know that speed = $\frac{Dis\tan ce}{Time}$

Total distance travelled by the wave in to and fro motion on a slinky $=2\times 10=20 \mathrm{m}$

Time taken= 10 sec.

Speed=  $=\frac{20}{10}=2 \mathrm{m}/\mathrm{s}$.

Hence, the velocity of wave is 2m/s.