Answer:
Work done to pull the piano upwards is 401250 J
Explanation:
Work is done against the gravity to pull the piano upwards
So here we can say that work done is

here we know that

also we know that
H = 75 m
now we have


Answer:
and 
Explanation:
The wavelength of a visible light is 727.3 nm.

The formula is as follows :

f is the frequency of the visible light

Energy of a photon is given by :
E = hf, h is Planck's constant

Red color has a frequency of
and energy per photon is
.
Answer:
v (speed) = S / t = 4 * 400 m / (6 * 60 sec) = 4.4 m/s
The average velocity is zero because there is no net vector displacement.
Summer does not start on the same day in every country on the earth