Question

In the 23rd century, an Earth probe to the planet Altair IV (mass 2.47x1024 kg, radius 3.12x106 m) has a communications failure. To request assistance, a small projectile is shot toward Earth from the surface of the planet, at speed 17.9x103 m/s (which is greater than the escape speed). Ignore friction and all other objects in the universe, and assume the projectile has no fuel. Find the speed of the projectile, in m/s, when it reaches Earth, which is far enough from Altair IV so the planet has negligible gravitational pull on the projectile (at r = ∞). Give your answer in scientific notation.

Answer 1

Use conservation of energy principle where the sum of potential and kinetic energy is constant for the projectile as shown below