MomentsAQA A-Level Maths: Mind map

Exam questions on Moments

1. A light plank is balanced horizontally on a smooth pivot. A child of mass $30$ kg sits $1.5$ m from the pivot on one side, and a second child of mass $m$ kg sits $2$ m from the pivot on the other side. Model both children as particles, with $g=9.8\ \text{m s}^{-2}$.
   Find the magnitude of the reaction of the pivot on the plank.2 marks
2. A non-uniform rod $AB$ of length $4$ m and mass $15$ kg is held horizontally in equilibrium by two vertical light strings attached at $A$ and $B$. The tension in the string at $B$ is $88.2$ N. Take $g=9.8\ \text{m s}^{-2}$.
   A particle of mass $5$ kg is attached to the rod so that the tensions in the two strings are equal. Find the distance of the particle from $A$.2 marks
3. A uniform beam $AB$ of length $5$ m and mass $50$ kg rests horizontally on two smooth supports at $C$ and $D$, where $AC=1$ m and $DB=1$ m. A man of mass $60$ kg stands on the beam at $E$, where $EB=0.5$ m. Model the man as a particle, with $g=9.8\ \text{m s}^{-2}$.
   Find the reaction of the support at $D$ on the beam.3 marks