Figure 13-44 gives the po- tential energy function U(r) of a projectile, plotted outward
from the surface of a planet of radius Rs. What least kinetic energy is required of a projectile launched at the surface if the
projectile is to “escape” the planet?

The astronauts on the space shuttle flights experienced an acceleration of 29 m/s2 (about 3 "g's") during lift-off. what upward force must the astronaut's seat apply to the astronaut in order to cause this acceleration? assume the astronaut's mass is 70 kg, and compute this force when the acceleration is near the earth's surface so their weight equals latex: mg m g .