I don’t know what you are trying to ask complete my but here are the steps to a scientific investigation i hope this helps you
At the present time, the only way we know of that light can get shifted
toward the blue end of the spectrum is the Doppler effect ... wavelengths
appear shorter than they should be when the source is moving toward us.
IF that's true in the case of the Andromeda galaxy, it means the galaxy is
moving toward us.
We use the same reasoning to conclude that all the galaxies whose light is red-shifted are moving away from us. That includes the vast majority of all galaxies that we can see, and it strongly supports the theory of the big bang
and the expanding universe.
If somebody ever comes along and discovers a DIFFERENT way that light
can get shifted to new, longer or shorter wavelengths, then pretty much all
of modern Cosmology will be out the window. There's a lot riding on the
Doppler effect !
<h2>QUESTION:- It is easier to lift the same load by using three pulley system than by using two-pulley system.</h2>
<h2>ANSWER:- IN CASE OF IDEAL PULLEY SYSTEM</h2>
<h2>REASON:- </h2>
Logic behind is lies behind the mechanical advantage of the provided bt the Pulley system.
as if we calculate the mechanical advantage of the 2 Pulley system we will have the value 2
And if we will calculate the mechanical advantage of the 3 pulley system then we will get the value of 3
so due to extra mechanical advantage we feel it easy to move with 3 pulley system then 2 Pulley system

If the current takes him downstream we must find the resultant vector of the velocities:

Then if the river is 3000 m-wide the swimmer will have to pass:
1.3520747 · 300 = 4056.14 m t = 4056.14 m : 1 m/s
a ) It takes
4056.15 seconds ( 1 hour 7 minutes and 36 seconds ) to cross the river.
b ) 0.91 · 3000 =
2730 mHe will be 2730 m downstream.