Concepts Of Physics MCQ Edition [Volume 1]PhysicsCentre of Mass, Linear momentum, Collision
The centre of mass of a body is located at the origin. The x -coordinates of the particles
Options
- Acould be entirely negative
- Bcould be entirely positive
- Ccould be entirely non-negative
- Dcould be positive for some particles and negative for others
Correct answer
D. could be positive for some particles and negative for others
Step-by-step solution
The x -coordinate of the centre of mass is given by X_ cm = m_i x_i m_i . Given X_ cm = 0 , we have m_i x_i = 0 . Since the mass of each particle is positive ( m_i > 0 ), the sum m_i x_i = 0 is possible only in two cases. First, x_i = 0 for all particles. In this case, all x -coordinates are zero, which means they are entirely non-negative. Second, some x_i > 0 and some x_i The x -coordinates cannot be entirely positive or entirely negative, as that would result in a non-zero centre of mass. Answer: could be entire