The last one, 12p 12e 12n
When we talk about that the sun rises and sets, an individual on the surface of the earth who is motionless or stationary is the spectator or observer. The observer may perhaps be on the moon to see that the sun does not travel all over Earth every 24 hours.
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
About 80 percent of sun reach earth surface