please i need help with this physics prob?

Question

One possible means of achieving space flight is to place a perfectly reflecting aluminized sheet into Earth 's orbit and use the light from the Sun to push this solar sail. Suppose such a sail, of area 5.60 104 m2 and mass 6300 kg, is placed in orbit facing the Sun. Ignore all gravitational effects, and assume a solar intensity of 1380 W/m2. (Hint: The radiation pressure by a reflected wave is given by 2 (average power per area)/c.)
(a) What force is exerted on the sail?
F = N
(b) What is the sail's acceleration?
a = m/s2
(c) How long does it take for this sail to reach the Moon, 3.84 108 m away?
t = days

Answer 1

Ok, it's a perfect reflecting solar sail, then :

The radiation pressure wil be : 2I / c

I = intensity of the wave

c = speed of light

and we know that the radiation pressure is : P = F / A

Radiation pressure = 2*1380 / 3*10^8

2*1380 / 3*10^8 = F / 5.60 104

F = 5.2 (Newtons)

b) Mass = 6300 kg

Usind Newton's second law :

5.2 = 6300*a

a = 8.25*10^-4 m/s^2

c) considering it has started from the rest :

D = 1/2*a*t^2

384108 = 1/2*8.25*10^-4*t^2

t = 30515 seconds

in days : one day has : 86400 seconds

t = 0.35 days

Hope that helps