Explanation:
Given that,
2 strings both vibrate at exactly 220 Hz. The frequency of sound wave depends on the tension in the strings.
The tension in one of them is then decreased sightly, then
will decrese.
Beat frequency, 

So, the new frequency of the string is 217 Hz. Hence, this is the required solution.
Answer:
The final kinetic energy is
Explanation:
From the question we are told that
The electric field is 
The charge on the object is 
The mass of the object is 
The distance moved by the object is 
The workdone on the object by the fields is mathematically represented as
![W = [qE + mg]d](https://tex.z-dn.net/?f=W%20%3D%20%20%5BqE%20%2B%20mg%5Dd)
Now this workdone is equivalent to the final kinetic energy so
![K = W = [qE + mg]d](https://tex.z-dn.net/?f=K%20%3D%20W%20%3D%20%20%5BqE%20%2B%20mg%5Dd)
substituting values
![K = W = [4.5*10^{-3 } *100 + 0.68 * 9.8]* 1](https://tex.z-dn.net/?f=K%20%3D%20W%20%3D%20%20%5B4.5%2A10%5E%7B-3%20%20%7D%20%2A100%20%20%2B%200.68%20%2A%209.8%5D%2A%201)

Answer:
0.02 s
Explanation:
Take the (+x) direction to be up.
The average velocity v during a time interval Δt is the displacement Δx divided by Δt.
v=Δx/Δt
=x_f-x_i/t_f-t_i (1)
We assume that your height is 1.6m
Solving [1]
Δt=Δx/v
= 0.02 s