Since the stone is being dropped, you know that it is in free fall. That means you can use your kinematics equations, since acceleration is free fall is a constant 9.8 m/s^2 down.
Looking through the kinematics equations, you want to use one that lets you find t, time, while using variables that we already know the values of. Notice that in the equation:

Say that the rock starts at point x=0. That means the initial value of x, the position, is

= 0m, and the final position is

= -4.9m. We are also told that the initial velocity,

= 0, assuming it's being dropped from rest, and a = -9.8 m/s^2. Plug these numbers in and solve for t:

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Answer: t = 1 s
Well, I think the answer would be 4 meters because the speed is in meters per second and the frequency is 5 waves every 2 seconds.
Wavelength = Speed/Frequency
I think the frequency is 2.5 waves a second but that's not something I'm 100% sure about.
I hope this helps though.
Hey There!
The atomic number represents the electrons and protons, therefore, if the atomic number of the element is 7 then there are 7 electrons and protons in the element.
In order to determine the amount of neutrons, you would subtract the atomic number from the atomic mass.
Hope this helped!
80/60=
1.3333...........................................