Answer:
An equipotential surface is circular in the two-dimensional. Since the electric field lines are directed radially away from the charge, hence they are opposite to the equipotential lines. Therefore, the electric field is perpendicular to the equipotential surface.
Angular frequency of pendulum is given by

for both pendulum we have


For other pendulum


now we have relate angular frequency given as
[tex\omega_1 - \omega_2 = 3.13 - 2.98 = 0.15 rad/s[/tex]
now time taken to become in phase again is given as


now number of oscillations complete in above time



Answer:
a. 0.275m/s
b. 1.08m
Explanation:
Since the duck the paddle the water at an interval of 1.6sec, we can determine the frequency of the wave formed using the equation
f=1/T
Where T is the period.
f=1/1.6
f=0.625Hz.
Also from the equation used in determining the speed of a wave
V=fλ,
v=0.625*0.2
v=0.125m/s
in the question it was stated that that the duck produce a wave moving at a speed of 0.40m/s.
Hence the speed of the duck is
v(duck)=0.40-0.125
v(duck)=0.275m/s
b. The distance between the crest behind the duck is the wavelength of the waves.
To determine this, the wavelength is expressed as
λ=v/f
but the speed in this case is the speed of the duck and the surface wave,as this account for the wave speed behind the duck,
Hence we have
λ=(0.40+0.275)/0.625
λ=1.08m.
The wavelength behind the duck is 1.08m