Answer:
3.3 mm
Step-by-step explanation:
The electric shaver is vibrating back and forward covering a distance of 2 mm, therefore, the amplitude of this vibration is always the half of the distance.
So the expression to use is:
A = D/2
A = 6.6 / 2 = 3.3 mm
Now, suppose you want the speed of this vibration:
V = 2πfA
V = 2π * 235 * 0.0033
V = 4.87 m/s