Astronomers use tiny wobbles of distant stars to detect the presence of planets orbiting those stars. this occurs because the star exerts a gravitational pull on the planet while the planet

  concave means having an outline or surface that curves inward like the interior of a circle or sphere. so the mirror curves inward.

Answer(b) both involve the use of levers;

Ke reqd to move from 0 to 50 will be proportional to 50x50 or 2500. this is equal to w.  to change vel from 50 to 150 you need energy prop to 22500 - 2500 = 20,000. this corresponds to 8w.  best answer is a) . work reqd is prop to velocity squared.