We are making an estimate based on a scene from a fictional story. We don't know the details of the star or the spacecraft. We also don't know if the sail is completely reflective, but we'll assume that it is. We'll find the net force exerted on the spacecraft and then use Newton's second law to find the direction of the acceleration. To find the net force, identify the source and direction of each force. Choose as many as apply. a. Light delivers momentum to the sail, much like a ball thrown at a wall delivers momentum to the wall. The ball's change in momentum is directed away from the wall, so the force on the ball is also directed away from the wall. By Newton's third law, then, the force on the wall is away from the person throwing the ball.
b. The spacecraft's thrusters are directed away from the star.
c. This spacecraft is propelled only by its sail.
d. The star's gravity is directed toward the star.
e. The star's light is directed away from the star.
f. The star's wind is directed away from the star.