Answer: The valve move 120° per second.
Explanation:
Since we have given a figure.
There is period of 2π in 3 seconds.
That means, it covers 2π degrees in every 3 seconds.
As we need to find the number of degrees the valve move per seconds.
We will use "Unitary method":
In every 3 seconds , Number of degrees would be 360°.
So, in every 1 second, Number of degrees would be

Hence, The valve move 120° per second.