A uniform beam long is pivoted at its centre

PHYSICS · Single correct · A Level · Physics · Mechanics and materials · Mechanics and materials

Problem

A uniform beam

60\,\text{cm}

long is pivoted at its centre. A

55\,\text{g}

mass is placed in the left pan attached at the

0\,\text{cm}

mark. The right pan at the

60\,\text{cm}

mark contains a

50\,\text{g}

mass. A

20\,\text{g}

rider can slide along the right half of the beam. At what distance from the pivot should the rider be placed to achieve balance? (a)

5\,\text{cm}

(b)

22.5\,\text{cm}

(c)

7.5\,\text{cm}

(d)

15\,\text{cm}