ROTATIONAL MOTION

How does the centre of mass of a uniform semicircular wire lie?

• At the centre of the circle
• At a point on the axis of symmetry, away from the diameter
• At the midpoint of the arc
• On the diameter

If a particle is at the origin, what is its contribution to ∑mi xi?

• Its full mass
• Zero
• mi times origin vector
• Undefined

What is the significance of the vector form R = (∑mi ri)/M in physics?

• It eliminates the need for mass
• It is only for 2D systems
• It provides a compact and general representation of the centre of mass
• It assumes zero gravity

How does the centre of mass of a system change if all positions are translated by the same vector?

• It remains fixed
• It translates by the same vector
• It doubles
• It becomes zero

What is the centre of mass of three particles of mass m at the vertices of an equilateral triangle of side a?

• At one vertex
• At the centroid, which is at a distance a/√3 from each vertex
• At the circumcentre, distance a/√2
• At the midpoint of a side