# Calculate the total momentum of the photons

## Homework Statement

The solar sail uses “radiation pressure” caused by the momentum of photons of sunlight as they strike the sail. A sail with an area of $1.5 \times 10^6 m^2$ could be used to propel a spacecraft of mass $1.2 \times 10^3 kg$.
The energy $E$ and momentum $p$ of a photon are related by the expression $E = pc$, where $c$ is the speed of light.
Calculate the total momentum of the photons striking $1 m^2$ of sail in one second. Assume the solar radiation flux (intensity) is $1400 W m^{-2}$.

## Homework Equations

$p=mv$?

## The Attempt at a Solution

Can I have hint's on how to approach this.

The momentum eqaution that I know is $p=mv$ but I don't think I can use this.