NASA often uses the gravity of a planet to slingshot a probe on its way to a more distant planet. The interaction of the planet and the spacecraft is a collision in which the objects do not touch. How can the probe have its speed increased in this manner? This problem confuses me, I want to use the conservation of momentum, but I can't really set it up, if I'm even going in the right direction. I could use some help with this problem. Thanks.