Chapter 27, Problem 79GP

To determine

The thrust that is experienced by spacecraft.

Answer to Problem 79GP

  $7N$ .

Explanation of Solution

Given:

Intensity of Sun light, $\text{I}=1000{\text{W/m}}^2$

Radius of spacecraft $=1km$

Formula used:

It is known that: $F=\frac{2IA}{c}$

Where,

  $F$ is the impulse or thrust.

  $I$ is intensity of light.

  $c$ is speed of light.

  $A$ is area of the object.

Calculation:

The thrust on the sail is due to change in momentum of the photons: $F=\frac{2IA}{c}$

  $\therefore F=\frac{2\times \left(1000{\text{W/m}}^2\right)\times {\left(1\times {10}^{3}m\right)}^2}{3.00\times {10}^{8}m/s}$

  $\therefore F=\frac{2\times \left(1000{\text{W/m}}^2\right)\times {\left(1\times {10}^{3}m\right)}^2}{3.00\times {10}^{8}m/s}$

  $\therefore F=7N\text{}$

Conclusion: The thrust that is experienced due to collision with the Sun’s photon is $7N$