(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A.P. French 6.8

A thrust-beam space vehicle works bearing a sort of sail which feels the push of a strong steady laser light beam directed at it from Earth. If the sail is perfectly reflected, calculate the mass of light required to accelerate a vehicle of rest mass [itex]m_0[/itex] up to a fixed value of [itex]\gamma[/itex].

2. Relevant equations

I usually define [itex]c=1[/itex] for convenience.

[itex]m'=m_o \gamma[/itex]

[itex]p = m_0v[/itex]

[itex]E = m_0c^2 = m'c^2+ q = E' + q[/itex] q is the energy of the photon(s) emitted

[itex]p=0=m'v - q/c = p' - q/c[/itex]

[itex]cp' = q[/itex]

3. The attempt at a solution

Since the sail is perfectly reflective I view as if the vehicle is emitting photons. Since it is accelerated to [itex]\gamma[/itex] we get [itex]v = \gamma[/itex] so [itex]p' = m'v = m_0 \gamma ^2[/itex]. Also [itex]q = m_0 \gamma ^2[/itex]

Honestly, I have little idea what I'm doing. I'm following French's book (Emission of photons p.177) and I keep running into dead ends. Any help would be appreciated.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Special Relativity - Relativistic Dynamics

**Physics Forums | Science Articles, Homework Help, Discussion**