The instantaneous velocity of the object is its speed and direction at that instant.
Answer
given,
Length of the string, L = 2 m
speed of the wave , v = 50 m/s
string is stretched between two string
For the waves the nodes must be between the strings
the wavelength is given by

where n is the number of antinodes; n = 1,2,3,...
the frequency expression is given by

now, wavelength calculation
n = 1

λ₁ = 4 m
n = 2

λ₂ = 2 m
n =3

λ₃ = 1.333 m
now, frequency calculation
n = 1


f₁ = 12.5 Hz
n = 2


f₂= 25 Hz
n = 3


f₃ = 37.5 Hz
As we know that electrostatic force between two charges is given as

here we know that electrostatic repulsion force is balanced by the gravitational force between them
so here force of attraction due to gravitation is given as

here we can assume that both will have equal charge of magnitude "q"
now we have



now we have

Its actually C. I did the question on USA test prep and it said the correct answer was C.
Answer:
The uncertainty in the location that must be tolerated is 
Explanation:
From the uncertainty Principle,
Δ
Δ

The momentum P
= (mass of electron)(speed of electron)
= 
= 
If the uncertainty is reduced to a 0.0010%, then momentum
= 
Thus the uncertainty in the position would be:
Δ
Δ