Density can be defined as the measure of mass of a substance per unit volume.
Answer
Mass m = 78 kg
Vertical height in each stage h = 11 m
(a).
Initial speed u = 0
Final speed v = 1.1 m / s


a = 0.055 m/s²
Work done




(b).Work done

W_b = 78× 9.8× 11

c)
Work done

Where V = final speed
= 0
v = 1.1 m / s
for deceleration a = -0.055 m/s²
now,

W_c = 545.75 × 11

Answer:
The distance from the radio station is 0.28 light years away.
Solution:
As per the question:
Distance, d = 4 ly
Frequency of the radio station, f = 854 kHz = 
Power, P = 50 kW = 

Now,
From the relation:
P = nhf
where
n = no. of photons/second
h = Planck's constant
f = frequency
Now,

Area of the sphere, A = 
Now,
Suppose the distance from the radio station be 'r' from where the intensity of the photon is 



Now,
We know that:
1 ly = 
Thus
