Question

Alice and Bob sit on a see saw, that consists of a uniform beam of mass 20kg and a fulcrum rock, that acts as a pivot point. The length of the beam is 8m. The mass of Bob is 70 kg and mass of Alice is 50 kg. How far from Bob should the pivot point be so that the see saw is balanced and does not move?

Answer 1

Answer:

Explanation:

Given

Mass of alice $M_a=50 kg$

Mass of bob $M_b=70 kg$

Mass of beam $M=20 kg$

Suppose fulcrum is at distance of d from bob thus From diagram

Equating torque i.e. torque of Bob,Alice and beam must cancel out each other to be balanced

$500\times (8-d)+20\times (4-d)=70\times d$

$400-50d+80-2d=70d$

$480=140d$

$d=\frac{480}{140}$

$d=3.43 m$