Two astronauts X and Y float in deep space far from external forces. Initially, they are at rest relative to one another. X throws a tool towards Y. Consider the two astronauts and the tool as one system. Which one of the following statements is correct ?
- A.The centre of mass of the system moves towards Y.
- B.X moves and the centre of mass of the system follows him.
- C.The centre of mass follows the tool.
- D.The centre of mass remains fixed.
Show answer
With no external force on the system, its centre of mass cannot start moving. The throw is an internal force: X pushes the tool forward and the tool pushes X backward with an equal and opposite force (Newton's third law).
Read the full explanation →