Final answer:
It is true that a solar sail craft can be propelled by particles in the solar wind. The statement that wave amplitudes only add up if they are propagating in the same line is false; amplitudes can add up due to superposition.
Step-by-step explanation:
Understanding Solar Sails and Wave Amplitudes
True or false: It is possible to propel a solar sail craft using just particles within the solar wind. The answer to this is true. Solar sails can indeed be propelled by the momentum of particles emanating from the Sun, which are part of the solar wind. They utilize the pressure exerted by these particles, much like a traditional sail uses the wind, to achieve propulsion.
Regarding the addition of wave amplitudes, the statement that 'The amplitudes of waves add up only if they are propagating in the same line' is false. Wave amplitudes can add up through the principle of superposition, irrespective of the direction in which they propagate. When two waves meet, their amplitudes can add together in both constructive and destructive interference, which doesn't require them to be in the same line.