A small spaceship whose mass is 1300 kg (including an astronaut) is drifting in outer space with negligible gravitational forces acting on it. If the astronaut turns on a 11 kW laser beam, what speed will the ship attain in 4.0 days because of the momentum carried away by the beam?

Explanation:

Relation between energy and momentum is as follows .

E = h c / λ

E / c = h / λ

h /λ = momentum of a photon

momentum of a photon  = E /c

= 11 x 10³ / 3 x 10⁸

= 3.67 x 10⁻⁵

In 4 days no of photon

= 4 x 24 x 60 x 60 = 345600 .

momentum of photon released

3.67 x 10⁻⁵  x 345600 .

= 12.68 kg m/s

This momentum will be imparted to spaceship .

12.68 = mv

12 .68 = 1300 x v

v = .00975 m /s

= 9.75 mm /s

explanation:

v=uf/(u-f)

= 5.-10/(5+10) convex lens has negative focal length