If plates are always in motion, why aren't we always having to redraw maps?

After the near spacecraft passed mathilde, on several occasions rocket propellant was expelled to adjust the spacecraft's momentum in order to follow a path that would approach the asteroid eros, the final destination for the mission. after getting close to eros, further small adjustments made the momentum just right to give a circular orbit of radius 45 km (45 × 10^3 m) around the asteroid. so much propellant had been used that the final mass of the spacecraft while in circular orbit around eros was only 545 kg. the spacecraft took 1.04 days to make one complete circular orbit around eros. calculate what the mass of eros must be.

There are two routes similar in terrain; however, one route has an incline of approximately 28 degrees, and you must decide on which route to take. what is the maximum road grade that your fully loaded ecv can climb?

Why is it important always to use horizontal bars in unit fractions when performing unit conversions?