the Doppler effect. (I don't know how to explain it lol)
Could it be "Scientific research"?
Answer:

Explanation:
The speed is by definition the distance traveled divided over the time it takes to travel that distance. In this case, this distance is the circumference of the wheel, so we have:

where we have written the circumference in terms of its radius.
For our values we then obtain the value:

Answer:
Time = t = 6.62 s
Explanation:
Given data:
Height = h = 215 m
Initial velocity =
= 0 m/s
gravitational acceleration = g = 9.8 m/s²
Time = t = ?
According to second equation of motion

As initial velocity is zero, So the first term of right hand side of above equation equal to zero.

t² = 
t =
t = 
t = 6.62 s
Answer: A while driving a car. It is unsafe