In order for a solar sail spacecraft to be accelerated to speeds ...

[Zoey63294]

In order for a solar sail spacecraft to be accelerated to speeds high enough to accomplish interstellar travel in a reasonable amount of time, it would need to be started
 
  A) from a lunar orbit where the gravity is weaker
  B) close to Earth using mirrors on the surface to reflect sunlight onto the sails
  C) far from the Sun so Jupiter could be used to help it on its way using a gravitational assist
  D) close to the Sun where the radiation pressure is higher

Question 2

Two children, each of mass 20.0 kg, ride on the perimeter of a small merry-go-round that is rotating at the rate of 1.0 revolution every 4.0 s. The merry-go-round is a disk of mass 30. kg and radius 3.0 m.
 
  The children now both move halfway in toward the center to positions 1.5 m from the axis of rotation. Calculate the kinetic energy before and after, and the final rate of rotation. Explain any changes in energy.

[cloudre37]

Answer to Question 1

D

Answer to Question 2

Ko = 0.61 kJ
Kf = 1.3 kJ
f = 0.55 Hz
Children do work moving inward.

[Zoey63294]

Wow, this really help

[patma1981]

Great answer, keep it coming