Granite is the answer i think
Answer:
The velocity of the tennis ball is 4.52 m/s.
Explanation:
Given that,
The distance covered by ball, d = 9.5 meters (due south)
Time, t = 2.1 sec
Let v is the velocity of the tennis ball. We know that the velocity of an object is given by the total distance covered divided by total time taken. It is given by :

So, the velocity of the tennis ball is 4.52 m/s. Hence, this is the required solution.
Metal detectors work by transmitting an electromagnetic field from the search coil into the ground. Any metal objects (targets) within the electromagnetic field will become energised and retransmit an electromagnetic field of their own.
The distance the spring stretches is the answer.
I hope this helps.
Have a nice day.