ROTATIONAL MOTION

What happens to the vector sum ∑mi ri if the origin is chosen at the centre of mass?

• It becomes infinite
• It becomes equal to total mass
• It becomes zero
• It doubles

How is the Y-coordinate of the centre of mass calculated for a system of three particles in a plane?

• Y = (y1 + y2 + y3)/3
• Y = (m1y1 + m2y2 + m3y3)/(m1 + m2 + m3)
• Y = m1y1 + m2y2 + m3y3
• Y = (m1 + m2 + m3)/(y1 + y2 + y3)

For three particles of equal mass not lying in a straight line, where does the centre of mass lie?

• At the circumcentre of the triangle
• At the orthocentre of the triangle
• At the centroid of the triangle formed by the particles
• Outside the triangle

What is the significance of the centre of mass in a system of particles?

• It is always at the geometric centre
• It is the point with maximum mass
• It represents the average position of mass in the system
• It is the point where velocity is zero

How is the X-coordinate of the centre of mass defined for a system of n particles along a straight line?

• X = ∑mi xi
• X = (∑mi xi)/M
• X = ∑xi/M
• X = M/(∑mi xi)